I noticed that I accidentally backed up a few hundred GB of log files for a few months in old snapshots. I need to keep these snapshots, but delete the accidentally added log files from them. Is this possible?
This is not possible, snapshots are immutable. They have to be, to ensure the integrity of backups.
Related to a similar, recent, post on the subject…
One way you might be able to do this is to write a script to restore each snapshot, delete the relevant files, set the system clock to when that backup ran, and then do a new backup to a fresh snapshot ID.
Iterate through all the IDs until complete. Then you could delete the old repository ID and cleanup with
Most chunks will already be in the backup storage so this is just about recreating snapshot metadata.
Obviously quite a bit involved but a suite of maintenance scripts to do this would be a worthwhile project IMO.