Hello,
There are two issues: first we do not correctly detect the time machine volume and we scan it by default even when the checkbox "Scan all Time Machine backups" is unchecked. This will be fixed in the 13.6 version.
But this does not fix the actual issue of scan taking too long for the case when the checkbox is checked; it seems that for some of the files in the local snapshot, read operation takes 15 seconds to start when the file is read for the first time. This can at this moment only be worked around by unchecking "Scan all Time Machine backups" checkbox.
Kind regards,
Ondrej Kolacek