cannot update mount namespace of snap "xyz"

[Detlef]

    Snap Refresh:

    Fehler: cannot perform the following tasks:
    - Sicherheitsprofile für Snap "audacity" (675) setzen (cannot update
    mount namespace of snap "audacity": cannot update preserved namespace of
    snap "audacity":
    -----
    update.go:85: cannot change mount namespace according to change unmount
    (/var/lib/snapd/hostfs/var/cache/fontconfig /var/cache/fontconfig none
    bind,ro 0 0): invalid argument
    update.go:85: cannot change mount namespace according to change unmount
    (/var/lib/snapd/hostfs/usr/share/fonts /usr/share/fonts none bind,ro 0
    0): invalid argument
    cannot update snap namespace: no such file or directory

D. Llewellyn <diddledan> wrote about:
This is a bug in snapd. It affects many snaps, not just Audacity.
Please file a bug on launchpad.net against snapd, so that those developers can fix it: https://bugs.launchpad.net/snapd/+filebug