Timeshift does not restore snapshots

Timeshift used to work on this very machine under UM. Now, selecting a (RSYNC-) snapshot for restore will start the entire procedure (comparing files, disclaimer…), but after rebooting the system ist just like before, nothing has been restored. I included /root and /home/username under „Filters“ and checked „include all“ under „Users“. I use UM 18.04 on a thinkpad t500. Can anybody help?!