While V3 and V4 are mixable,they are still a bit different so I guess it’s to be expected that things may not work the same way. That being said I understand your frustration, a third of the prints I make are “standard parts” for our internal needs and I take the time to fine-tune the parts and the prints, only to face a failure when changing tanks or resin version.
From your V3 print though, it looks like the part was already affected by the issues and V4 only aggravated it. It seems to me you tried to push the printer to its limits in terms of supports density and the limit isn’t the same with V4.