Recently our daemons crashed due to this:
{P1207}
The task `PHID-TASK-tethsf3ggl7b527jd2uu` had a very long title - 324 chars long. I haven't looked into the code, but quick glance at db schema showed that `maniphest_task.originalTitle` field is of type `TEXT`, while `search_document.documentTitle` is a `VARCHAR(255)`. I guess this might be the culprit.
Now, I haven't worked with Phabricator migrations and the search infrastructure, so I didn't fix it myself, but I hope this helps if someone else encounters similar problem or knows more about relevant code.
It seems that changing Maniphest task name to a short one and restarting daemon remedied the problem.
Overall, I'd say we hit a quite rare edge case here.