I'm seeing a couple of things:

1. Create a new message. My default forum is Visual FoxPro. If I change the Forum to "Universal Thread", it takes a few seconds for the Category dropdown to update. If during that time I click on the Category dropdown, I still get the categories for VFP, even when the Forum has updated to Universal Thread. I can't get the Category dropdown to work as expected unless I manually switch to some other Forum, let the Categories update, then switch back to UT, and let the Categories update again.

Maybe the Categories dropdown should be disabled while its contents are being updated?

2. A little while ago I created another message about auto quote. While I was composing that message, I couldn't remember exactly what the reply option was, so I opened a forum message in another tab and started a reply, so I could see the reply options.

When I switched back to the tab where I was composing my auto quote message, the Forum and Category had changed to the default values I get when creating replies (probably as a result of starting a reply in the other tab).

I would expect message composition in multiple tabs to be independent and not overwrite one to another.