That error usually indicates a problem on the host creating the backup. (Or in some cases on the host running the checks. Does restic check --read-data-subset 95/256 continue to return that error?).
This error can only occur when the affected blob was damaged during creation of the pack file (or while checking it). This is usually caused by bitflips in memory, so please run a memtest on the affected host. Which kernel version are you using? There have been problems with older version of Linux 5.2-5.4, see also Troubleshooting unreproducible consistency errors - #19 by cyounkins.
Repairing the repository would then either amount to following the steps in Hash does not match id during prune · Issue #1999 · restic/restic · GitHub or to use restic find --pack 5ef6ac9a to find the affected snapshots and remove them.
apt-get uses the latest version packaged for your distribution. That version is frequently older than the latest version available for some software.
restore expects a snapshot ID, and cat blob expects a blob ID. The ID returned by check is a pack ID.