It seems to happen every few days at least. First time it happened - if I can trust the log search (which I can’t as described here) - was on Fri 18th Nov 2022.
It happens in production. I haven’t tried to replicate it with a minimal example yet.
It also sometimes happens when anvil.users.login_with_form(allow_cancel=True) is called from inside my main form module.
RuntimeError: This component is already added to a container, or is already inside an alert
at anvil-services/anvil/users/__init__.py, line 556
called from Nav, line 392
called from Nav, line 293
called from Nav, line 88