MR page DOM not updated by server-side changes

On gitlab.torproject.org, I observe that an MR web page that I have open is dynamically updated when the state changes.

But on salsa.debian.org, this doesn't happen. The most obvious scenario is submitting an MR review, which on gitlab.t.p.o causes the whole page to reflect the new state, with all the comments made non-draft, etc. On salsa.d.o the MR finalisation comment seems to vanish.

Reloading the page "fixes" it by causing display of the current information - but, again, it is not updated in response to further changes.

I think this used to work on salsa.d.o, but has been broken for some time - months, at least. I suspect this may be the same issue as #444.

It would be nice if this could be fixed. It looks like it might need some reconfiguration of the web frontend proxy, or something?