I have the same problem for a long time.
Working on iMac Pro (Intel) and QNAP server.
I'm saving the auto backup copies on local HD, and it was working better then saving them on the QNAP.
BUT!!! Now these backup files also have this problem and I can't open neither one of them. This is really bad bad situation....
C4D 2025.2.1 Redshift 2025.4.2 iMacPro 2.3 GHz 18-Core Intel Xeon W