The RemoveUnreferencedRows script does not check whether artist credits have pending edits before removing them. As long as the ref_count is 0 (so, they're not in use yet), it will remove a credit that has an open edit changing it (which could cause it to redirect instead) or applying it to a release track or whatnot.

My understanding is that the removal won't affect the edit if it was just using the credit (a new credit will be created to replace the removed one) but it's still not ideal to lose the MBID in this case. And of course, I'd expect any edits editing the newly-removed credit to just fail.