UAIPerceptionSystem::UnregisterSource according to its documentation should treat Sense == null as targeting all sources, but the code for removing pending sources does not treat Sense == null as this.
The source is not removed, because the pending pass does not treat Sense == null as targeting all senses.
Expected: The source should be removed. As per the documentation of the function, Sense == null should be treated as targeting all senses.
Code to repro:
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-156745 in the post.