Yes, sir DragonFish I uploaded details of the last time it occurred here. Active Directory corruption
Pretty much the only difference I noticed this time is it recurred after stripping ACLs and reapplying on the next day, and did not reoccur after clearing the AD cache but I have no real evidence that is related for sure.
I am going to test Electric Eel on my home setup but that is pretty much just Truenas SMB + Emby without AD.