This is pretty bad. I think your wallet.dat is missing the private keys of the zpiv accumulated. The same thing has happened to me with version 3.0.0. Luckily I was missing 100 zpiv only. Since I was restarting the client during this time I had several backups of my wallet. Restoring an older version, which was created right after those zpiv where converted, restored them.

Maybe there is a console command to dump your zpiv private keys? Is it the usual listaddressgroupings/dumpprivatekey? This would allow to inspect your wallet backups for new private keys, which are missing in your wallet.dat. Just make sure you don't overwrite your current wallet.dat without creating a backup, when your client is stopped!