Running firefox instance malfunctions after refresh of gnome-42-2204 snap

I noticed that my running instance of Firefox had become unstable, unable to load new pages and other malfunctions. According to "snap changes", the gnome-42-2204 snap had been updated overnight:

    $ snap changes
    ID Status Spawn Ready Summary
    762 Done yesterday at 23:56 AWST yesterday at 23:56 AWST Auto-refresh snap "gnome-42-2204"
    763 Done today at 11:41 AWST today at 11:41 AWST Auto-refresh snap "gnome-calculator"

In the journal, there were errors like:

    Apr 15 13:06:41 scruffy firefox_firefox.desktop[1434016]: ERROR: ld.so: object '/snap/firefox/2517/gnome-platform/$LIB/bindtextdomain.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
    Apr 15 13:06:41 scruffy firefox_firefox.desktop[1434016]: XPCOMGlueLoad error for file /snap/firefox/2517/usr/lib/firefox/libmozgtk.so:
    Apr 15 13:06:41 scruffy firefox_firefox.desktop[1434016]: libgtk-3.so.0: cannot open shared object file: No such file or directory
    Apr 15 13:06:41 scruffy firefox_firefox.desktop[1434016]: Couldn't load XPCOM.
    Apr 15 13:06:41 scruffy firefox_firefox.desktop[1300987]: [Parent 1300987, IPC I/O Parent] WARNING: process 1434016 exited with status 255: file /build/firefox/parts/firefox/build/ipc/chromium/src/base/process_util_posix.cc:272

Looking at the running process's mount namespace, /proc/$pid/root/snap/firefox/2517/gnome-platform was empty, which accounts for the missing library errors. If I started a new process using firefox's sandbox settings with "snap run --shell firefox", that gnome-platform directory was correctly populated.

So the main persistent mount namespace for the snap was correctly updated. The problem is that the cloned namespace the app actually runs in (it's using the desktop interface, so runs in a separate namespace to set up $XDG_RUNTIME_DIR/doc) seems to have gotten out of sync, with not all changes from the parent namespace propagating. In particular, there was nothing mounted under /snap/firefox/2517/gnome-platform according to /proc/$pid/mountinfo.

ProblemType: Bug
DistroRelease: Ubuntu 23.04
Package: snapd 2.59.1+23.04ubuntu1
ProcVersionSignature: Ubuntu 6.2.0-18.18-generic 6.2.6
Uname: Linux 6.2.0-18-generic x86_64
ApportVersion: 2.26.1-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Sat Apr 15 13:19:38 2023
InstallationDate: Installed on 2021-03-28 (747 days ago)
InstallationMedia: Ubuntu 21.04 "Hirsute Hippo" - Alpha amd64 (20210327)
RebootRequiredPkgs: Error: path contained symlinks.
SnapChanges: no changes found
SourcePackage: snapd
UpgradeStatus: Upgraded to lunar on 2023-03-19 (26 days ago)