Comment 16 for bug 1616629

@zyga: I'm seeing this when there was a previous failed attempt at refreshing and/or removing (not sure which). The mount table has been somehow corrupted, whereby mount thinks that the snap is mounted, but umount thinks that it is not, and refuses to unmount it: https://pastebin.ubuntu.com/p/NGsc2yp7Sr/

Interestingly, a reboot does not correct the problem with the mount table. Is snapd perhaps recreating this state on boot?