Uncaught exception thrown in session handler.

Drupal\Core\Database\DatabaseExceptionWrapper: SQLSTATE[40001]: Serialization failure: 1213 Deadlock found when trying to get lock; try restarting transaction: INSERT INTO "nlp_sessions" ("sid", "uid", "hostname", "session", "timestamp") VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4); Array ( [:db_insert_placeholder_0] => lPP2ZJIOqlcAcCvcT4Btuj_b9kJdcARS4VecdFZwAmY [:db_insert_placeholder_1] => 0 [:db_insert_placeholder_2] => 172.23.0.2 [:db_insert_placeholder_3] => _symfony_flashes|a:1:{s:5:"error";a:1:{i:0;O:25:"Drupal\Core\Render\Markup":1:{s:9:"*string";s:7088:"<em class="placeholder">Deprecated function</em>: json_decode(): Passing null to parameter #1 ($json) of type string is deprecated in <em class="placeholder">Drupal\mathjax\Plugin\Filter\MathjaxFilter-&gt;process()</em> (line <em class="placeholder">44</em> of <em class="placeholder">modules/contrib/mathjax/src/Plugin/Filter/MathjaxFilter.php</em>). <pre class="backtrace">Drupal\mathjax\Plugin\Filter\MathjaxFilter-&gt;process(&#039; The challenge targets information extraction from Spanish radiology reports, and aims at providing a standard evaluation framework to contribute to the advancement in the field of clinical natural language processing in Spanish.&#039;, &#039;en&#039;) (Line: 118) Drupal\filter\Element\ProcessedText::preRenderText(Array) call_user_func_array(Array, Array) (Line: 101) Drupal\Core\Render\Renderer-&gt;doTrustedCallback(Array, Array, &#039;Render #pre_render callbacks must be methods of a class that implements \Drupal\Core\Security\TrustedCallbackInterface or be an anonymous function. The callback was %s. See https://www.drupal.org/node/2966725&#039;, &#039;exception&#039;, &#039;Drupal\Core\Render\Element\RenderCallbackInterface&#039;) (Line: 788) Drupal\Core\Render\Renderer-&gt;doCallback(&#039;#pre_render&#039;, Array, Array) (Line: 374) Drupal\Core\Render\Renderer-&gt;doRender(Array, ) (Line: 204) Drupal\Core\Render\Renderer-&gt;render(Array) (Line: 479) Drupal\Core\Template\TwigExtension-&gt;escapeFilter(Object, Array, &#039;html&#039;, NULL, 1) (Line: 88) __TwigTemplate_46cf2cb5ce1e020fec29c3375b8ffc02-&gt;doDisplay(Array, Array) (Line: 405) Twig\Template-&gt;displayWithErrorHandling(Array, Array) (Line: 378) Twig\Template-&gt;display(Array, Array) (Line: 46) __TwigTemplate_324600d6877321ff2411db6617d8bf05-&gt;doDisplay(Array, Array) (Line: 405) Twig\Template-&gt;displayWithErrorHandling(Array, Array) (Line: 378) Twig\Template-&gt;display(Array, Array) (Line: 43) __TwigTemplate_116241b0c54beaa065c54503470a35e2-&gt;doDisplay(Array, Array) (Line: 405) Twig\Template-&gt;displayWithErrorHandling(Array, Array) (Line: 378) Twig\Template-&gt;display(Array) (Line: 390) Twig\Template-&gt;render(Array) (Line: 55) twig_render_template(&#039;core/themes/classy/templates/field/field--text-long.html.twig&#039;, Array) (Line: 384) Drupal\Core\Theme\ThemeManager-&gt;render(&#039;field&#039;, Array) (Line: 433) Drupal\Core\Render\Renderer-&gt;doRender(Array, ) (Line: 204) Drupal\Core\Render\Renderer-&gt;render(Array) (Line: 479) Drupal\Core\Template\TwigExtension-&gt;escapeFilter(Object, Array, &#039;html&#039;, NULL, 1) (Line: 80) __TwigTemplate_038e0db2e394f2fab4504226b512a0bb-&gt;block_content(Array, Array) (Line: 182) Twig\Template-&gt;displayBlock(&#039;content&#039;, Array, Array) (Line: 68) __TwigTemplate_038e0db2e394f2fab4504226b512a0bb-&gt;doDisplay(Array, Array) (Line: 405) Twig\Template-&gt;displayWithErrorHandling(Array, Array) (Line: 378) Twig\Template-&gt;display(Array) (Line: 390) Twig\Template-&gt;render(Array) (Line: 55) twig_render_template(&#039;core/themes/classy/templates/block/block.html.twig&#039;, Array) (Line: 384) Drupal\Core\Theme\ThemeManager-&gt;render(&#039;block&#039;, Array) (Line: 433) Drupal\Core\Render\Renderer-&gt;doRender(Array) (Line: 446) Drupal\Core\Render\Renderer-&gt;doRender(Array, ) (Line: 204) Drupal\Core\Render\Renderer-&gt;render(Array) (Line: 479) Drupal\Core\Template\TwigExtension-&gt;escapeFilter(Object, Array, &#039;html&#039;, NULL, 1) (Line: 54) __TwigTemplate_fd1f67f696427df30219cdb6a6f6c651-&gt;doDisplay(Array, Array) (Line: 405) Twig\Template-&gt;displayWithErrorHandling(Array, Array) (Line: 378) Twig\Template-&gt;display(Array) (Line: 390) Twig\Template-&gt;render(Array) (Line: 55) twig_render_template(&#039;core/themes/stable/layouts/twocol_section/layout--twocol-section.html.twig&#039;, Array) (Line: 384) Drupal\Core\Theme\ThemeManager-&gt;render(&#039;layout__twocol_section&#039;, Array) (Line: 433) Drupal\Core\Render\Renderer-&gt;doRender(Array) (Line: 446) Drupal\Core\Render\Renderer-&gt;doRender(Array) (Line: 446) Drupal\Core\Render\Renderer-&gt;doRender(Array, ) (Line: 204) Drupal\Core\Render\Renderer-&gt;render(Array) (Line: 479) Drupal\Core\Template\TwigExtension-&gt;escapeFilter(Object, Array, &#039;html&#039;, NULL, 1) (Line: 67) __TwigTemplate_1203672ee210fd6187b767a3291e5c83-&gt;doDisplay(Array, Array) (Line: 405) Twig\Template-&gt;displayWithErrorHandling(Array, Array) (Line: 378) Twig\Template-&gt;display(Array) (Line: 390) Twig\Template-&gt;render(Array) (Line: 55) twig_render_template(&#039;core/themes/classy/templates/content/taxonomy-term.html.twig&#039;, Array) (Line: 384) Drupal\Core\Theme\ThemeManager-&gt;render(&#039;taxonomy_term&#039;, Array) (Line: 433) Drupal\Core\Render\Renderer-&gt;doRender(Array) (Line: 446) Drupal\Core\Render\Renderer-&gt;doRender(Array, ) (Line: 204) Drupal\Core\Render\Renderer-&gt;render(Array) (Line: 479) Drupal\Core\Template\TwigExtension-&gt;escapeFilter(Object, Array, &#039;html&#039;, NULL, 1) (Line: 72) __TwigTemplate_9ba5c633675d21d66101f263a0219466-&gt;doDisplay(Array, Array) (Line: 405) Twig\Template-&gt;displayWithErrorHandling(Array, Array) (Line: 378) Twig\Template-&gt;display(Array) (Line: 390) Twig\Template-&gt;render(Array) (Line: 55) twig_render_template(&#039;core/themes/classy/templates/views/views-view.html.twig&#039;, Array) (Line: 384) Drupal\Core\Theme\ThemeManager-&gt;render(&#039;views_view&#039;, Array) (Line: 433) Drupal\Core\Render\Renderer-&gt;doRender(Array) (Line: 446) Drupal\Core\Render\Renderer-&gt;doRender(Array, ) (Line: 204) Drupal\Core\Render\Renderer-&gt;render(Array, ) (Line: 242) Drupal\Core\Render\MainContent\HtmlRenderer-&gt;Drupal\Core\Render\MainContent\{closure}() (Line: 580) Drupal\Core\Render\Renderer-&gt;executeInRenderContext(Object, Object) (Line: 243) Drupal\Core\Render\MainContent\HtmlRenderer-&gt;prepare(Array, Object, Object) (Line: 132) Drupal\Core\Render\MainContent\HtmlRenderer-&gt;renderResponse(Array, Object, Object) (Line: 90) Drupal\Core\EventSubscriber\MainContentViewSubscriber-&gt;onViewRenderArray(Object, &#039;kernel.view&#039;, Object) call_user_func(Array, Object, &#039;kernel.view&#039;, Object) (Line: 142) Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher-&gt;dispatch(Object, &#039;kernel.view&#039;) (Line: 174) Symfony\Component\HttpKernel\HttpKernel-&gt;handleRaw(Object, 1) (Line: 81) Symfony\Component\HttpKernel\HttpKernel-&gt;handle(Object, 1, 1) (Line: 58) Drupal\Core\StackMiddleware\Session-&gt;handle(Object, 1, 1) (Line: 48) Drupal\Core\StackMiddleware\KernelPreHandle-&gt;handle(Object, 1, 1) (Line: 106) Drupal\page_cache\StackMiddleware\PageCache-&gt;pass(Object, 1, 1) (Line: 85) Drupal\page_cache\StackMiddleware\PageCache-&gt;handle(Object, 1, 1) (Line: 48) Drupal\Core\StackMiddleware\ReverseProxyMiddleware-&gt;handle(Object, 1, 1) (Line: 51) Drupal\Core\StackMiddleware\NegotiationMiddleware-&gt;handle(Object, 1, 1) (Line: 23) Stack\StackedHttpKernel-&gt;handle(Object, 1, 1) (Line: 713) Drupal\Core\DrupalKernel-&gt;handle(Object) (Line: 19) </pre>";}}}_sf2_meta|a:3:{s:1:"u";i:1772263376;s:1:"c";i:1772263376;s:1:"l";i:2000000;} [:db_insert_placeholder_4] => 1772263376 ) in Drupal\Core\Session\SessionHandler->write() (line 87 of /opt/drupal/web/core/lib/Drupal/Core/Session/SessionHandler.php). 

Drupal\Core\Session\SessionHandler->write() (Line: 95)
Drupal\Core\Session\WriteSafeSessionHandler->write() (Line: 73)
Symfony\Component\HttpFoundation\Session\Storage\Proxy\SessionHandlerProxy->write()
session_write_close() (Line: 304)
Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->save() (Line: 196)
Drupal\Core\Session\SessionManager->save() (Line: 191)
Symfony\Component\HttpFoundation\Session\Session->save() (Line: 61)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 23)
Stack\StackedHttpKernel->handle() (Line: 713)
Drupal\Core\DrupalKernel->handle() (Line: 19)

The website encountered an unexpected error. Please try again later.
RuntimeException: Failed to start the session because headers have already been sent by "/opt/drupal/web/core/lib/Drupal/Core/Session/SessionHandler.php" at line 96. in Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() (line 152 of /opt/drupal/vendor/symfony/http-foundation/Session/Storage/NativeSessionStorage.php). 
Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() (Line: 162)
Drupal\Core\Session\SessionManager->startNow() (Line: 110)
Drupal\Core\Session\SessionManager->start() (Line: 57)
Symfony\Component\HttpFoundation\Session\Session->start() (Line: 240)
Drupal\big_pipe\Render\BigPipe->performPreSendTasks() (Line: 295)
Drupal\big_pipe\Render\BigPipe->sendContent() (Line: 112)
Drupal\big_pipe\Render\BigPipeResponse->sendContent() (Line: 381)
Symfony\Component\HttpFoundation\Response->send() (Line: 20)