MediaWiki version: 1.35.0-wmf.39
$entityId and $targetId must refer to the same kind of entity.
Quite a bit of logspam from this one in production logstash for wmf.39
This happens for both Forms and Senses.
- Exception doesn't surface to user & is not logged
- User gets a useful response (see comments, either a message or 303 or something similar)