Yesterday, I updated a site from latest-release +19 to latest. All went well, except I myself started getting lots of notifications about group messages for a group I am not in. I looked at the group inbox and the button to change notification level is not displaying correctly. I tried safe mode and there was no change. I also rebuilt again, with no luck.
It looks like this:
When I select it and choose “normal” I get this in the javascript console:
On another site I manage, the button looks like the below and when I change notification level no error appears in the console. Though I did notice the icon sometimes disappears - I think that is a known separate issue.
Quick followup - a fellow staff member on that forum pointed out to me that the helpdeskteam group is getting multiple notifications about the same notification event. This is pretty weird! This is the same group I am having trouble with as explained in OP.
