I have nothing against Mission Control but don't use it much except now when my secondary click opens it every the time.
I usually want the secondary click to open a context window like I now have to do with the ctrl single click.
On my trackpad I use the two finger tap as secondary click as per below settings. With a mouse it's the right button. In both cases Mission Control is opened instead of a context window.
For full disclosure I mention that I make use of BetterSnapTool and Alfred3 but when I unload them the issue persists.
Best Answer
As a troubleshooting step I would start with booting into Safe Mode to see if the behaviour is replicated there, and also to see if the behaviour continues again afterwards when you've logged back in normally.
Boot into Safe Mode
Follow these steps to boot your Mac into Safe Mode:
Once you've booted into Safe Mode, let me know how you went and we'll go from there.
Trash your Mission Control preferences
Now that we know the problem isn't caused by a 3rd party extension etc, let's trash the preferences for Missopn Control and see what changes that maes.
com.apple.spaces.plist
and move it to TrashNow test again and let me know how you went and we'll go from there.