The Advanced setting "Release channel" is not respected

Hi!

I did set my 1Password 8 App to the "nightly" builds channel a few weeks ago. At present, I am running:

1Password for Mac 8.11.22 / 81122010, on NIGHTLY channel
My advanced setting for the channel is: PRODUCTION / install updates automatically

When I click the "Check for updates" button in the About panel, always a new nightly build is installed. I just got 81122010 a few minutes ago.
I also tried to set to BETA, but no new beta build has been installed for weeks, although new beta versions were announced on the website.

How can I make sure that 1P does really install builds from the correct (selected) update channel?