If I change code in EntityQueryTest:141  from 

          list($field_name, $langcode, $values) = $units[$key];
          $entity->getTranslation($langcode)->{$field_name}[] = $values;

to

          list($field_name, $langcode, $values) = $units[$key];
          $entity->getTranslation($units[$key][1])->{$units[$key][0]}[] = $units[$key][2];


It works fine. I've tried to produce a snippet that just does the list() and cause the error but I've not been successful yet.

Also Grav (www.getgrav.org) unit tests fail if opcache is turned on, but run just fine if opcache is turned off. Similar issues can be seen in the sites as well (which also work without opcache just fine).

All the issues seem to be related to Pimple, or offsetGet($id) call which seems to have more or less random value $id passed to it. Sometimes $id = '', sometimes the value of the $id comes from a previous offsetGet() call and once it even had value from the following method call $this->initializeController().. Meaning that the $id = 'initializeController', not $id = 'task' as written in the code. For some reason in the last case making a random change (adding a whitespace) in the affected file fixes the issue until opcache gets cleared.

I'm not sure if the issues are related, is $units an ArrayAccess object?

@matias: At least in your case, you're probably hitting bug #77275, which will be fixed in the next release.

Yes, I just confirmed that the issue gets fixed by adding this option to php.ini:

opcache.optimization_level=0x7FFFBBFF

Thank you @nikic!

Is the Drupal test still failing with any of the actively
supported PHP versions[1]?

[1] <https://www.php.net/supported-versions.php>

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