Change host should invalidate the old host

Good spot.

Cache::invalidateTags([$old_host_entity->getRegistrationListCacheTag()]);

FWIW I would have done this in Registration::postSave().

Yep I had it there first, but moved it because I didn't want the overhead on every registration save for what will be quite rare.

Automatically closed - issue fixed for 2 weeks with no activity.