NodeBB's cache buster is based on its current git hash (so if you've upgraded it will try to send you the new CSS and JS, which works well, but it remains the same if switching themes, which results in your issue)
I suppose the dev team hasn't run into this because we usually run with cache disabled while testing (and because Persona is so awesome so why switch? Kidding)
Hmm, I also noticed that a new user account registration was pending approval, but a click on the little red indicator icon lead to no redirection. Only something like "show all notifications" finally showed me the approval queue, where than a click on the green icon also lead to no further actions. Seems the Admin panel is a bit shaky now. NodeBB runs inside VMware, no crash or so happened with weekly backups of the VM.
The core forum functions are working, so no big deal. If it falls apart I report back 😁