Perhaps the main file became corrupted and you ran a backup routine to copy the corrupted file to the 3 backup locations?
The cloud service would probably have caught that for that copy.
No. There were all hand copied and each one was checked after copy. Also, the hard drives showed the file existed in the directory but all the data was removed. I could’t use any of my data recovery tools to get the file back. I used a disk editor to look at the file as well and it was precisely zeroed out. Been in tech since I was a kid and I’ve never seen a damaged file like it... and on three drives and removed from cloud.