Tom C,
Just so you know, it was not the mob going through that caused this. the lead is broken when you or the mob enter the portal. The dropped lead (item entity) is what gets in the portal and caused the crash. it you shove the horse in an then follow him afterwards, it wont happen.
I have had this happen to me as a player. However, it did not crash the server, but when i entered the portal (after the cow already TPed), I came out at a different portal.. a WAY different portal. My overworld portal where I sent the cow was at -23000 x and 17000 z... i was tped to nether coords something like 200, 300 and when I went back in portal, I emerged at someones home near spawn...
Not really a duplicate... 73866 is specific about "snowballs" (moving entity that does not drop), whereas mine is about drops from inventory (any item). Also, I included the server crash file.. 😞.. hopefully I can post my crash files to that report??
No, and at this point, I don't think the problem exists anymore.. Can you close this?