Update: the two referenced blobs, p5a59d… and p5a596… are both zero bytes. Is there any way to either recover these or determine which snapshots they belong to? If they are old versions of files, I would prefer to drop that snapshot rather than restart the entire backup from scratch.
Edit: I attempted to use kopia content delete to remove the contents I didn’t have valid blobs for, accepting the data loss. However, then kopia maintenance run --full completed with:
ERROR snapshot GC failure: error running snapshot gc: error iterating contents: Could not undelete referenced content: {a��+��♣�↓��↓�� 0315933df5321eb1a7d729b3ec26fdcb 0xc00037a480}: unable to get content data and info: error getting cached content: BLOB not found
Following this thread, I re-snapshotted everything with --force-hash=100. The full maintenance still did not complete successfully - it appears I am unlucky and an altered file was corrupted, so unless this issue is implemented I will continue having GC errors.