I am also experiencing this problem. Two unrelated things:
I previously, back in June or July if memory serves me well, “forced” an upgrade by temporarily switching channels. Could this in any way be the reason? I could do that again but would like to know and maybe help if the problem lies elsewhere.
Nextcloud could make the gradual rollout procedure of upgrades more visible (on website, in release communication, top of forum) and more clear (has rollout been completed, what percentage has been serviced, has rollout been stopped for whatever reason)