Scrub should have fixed it in case it could do that (won'T work with single disk or raid0 because mirrors or parity data is required for that).
PBS could mark that chunk as corrupted so PVE would upload it again (only in case the data of that chunk still exists on the PVE) next time backup up a VM that uses this chunk. But for that PBS needs to know that the chunk got corrupted and for that you would need to run verify task forcing a re-verify of all backup snapshots.