I have a very strange problem, and it started since I got my LG 5K Ultrafine screen and started using an external keyboard and mouse.

I usually notice it in Blender, so it might be related to that.

I use the middle mouse button to rotate the view in Blender, and suddenly it acts as if I'm holding down the mouse button, even if I'm not, and when I move the mouse the view rotates.

Now if I switch to a browser, like Chrome, the middle mouse button doesn't work. I can't close tabs for example, which usually works.

Using the track pad, I can triple finger click, and it works as it should.

I have a couple of mouse controlling apps, to make it work like I'm used to from PC, and it might be causing these issues.

* Smart scroll (to controll scroll speed in different apps)
* USB overdrive (to disable the horrible acceleration)
* Logitech control center (which only works when a Logitech mouse is in)

I just tried switching to a Logitech mouse, and it has the same issues as the other mouse, which is a Corsair (which doesn't have Mac drivers, but it usually just works)

Suddenly it just starts working again, and also a reboot helps, but it's so annoying since it happens like once every 30 minutes or so.

So it's a weird problem, and I'd be happy to know if anyone has had anything similar?