Under certain circumstances, when a server config is broken (a regression, wrong config or anything else) - the Index entity throws SearchApiException while trying to retrieve server info an index is attached to. The exception is not handled anywhere and brings the entire site down.
The following message is then displayed:
The website encountered an unexpected error. Try again later.
Drupal\search_api\SearchApiException: The server with ID 'server name' could not be retrieved for index 'index_label'. in Drupal\search_api\Entity\Index->getServerInstance() (line 505 of modules/contrib/search_api/src/Entity/Index.php).
Not sure, as this happened randomly and was quickly fixed with disabling and re-enabling the server in question.
Handle the exception and report an error in the watchdog.
Active
1.35
General code
Sorry, but without further information about the stack trace it won’t be possible to fix this. We already try to catch exceptions wherever they may occur, so if we missed one place it will be very hard to find.