I found a possible fix.
1 - Go to game configuration and set mouse x and y sensivity to maximum, then close the game.
2 - Now go to your windows mouse properties >>> Pointer Options and reduce your pointer speed.
Now open the game and check if your current mouse speed is playable for you, if not, reduce your pointer speed even more but do not touch on your game mouse configuration, that must be set to maximum at always.
You're on to something here, this certainly helped so thank you. Altough I maxed out both mouse X and Y sensitivity, I didn't lower OS's mouse pointer speed. My mice isn't even very "gaming" mice, but it has 7 levels of DPI switchable on the fly. I'm always using 5th level and somehow, I managed to get the game to deal with it, because once I did at least 2-3 full cycles of switching from 1st to 7th level of Dpi with the game running, slowdown/stickyness in Log/Objectives screen is practically gone, even in Main Menu. If anything, very rarely will you see it struggling a tad but that's it.
If your mice supports multiple DPI presets, try using that - it might save you trouble of adjusting your OS's pointer sensitivity back when you're done playing.
While my present mouse doesn't support multiple DPI settings, I will try this out. So it's a matter of setting in-game sensitivity to high, closing it, and setting windows mouse sensitivity low?
What do you mean by sticky mouse controls ? Can you explain it in-depth so I can try reproducing this on my computer ? Personally I've never had any mouse problems but yours may be due to using a too complicated mouse (like a gaming one) so that the old DirectInput system cannot handle it properly.
A lot of people are having it, me included. So what it is is essentially a hang-up of sorts on mouse input in-game, that happens often, albeit randomly. What it does for me is seemingly drop a massive deadzone in one or two parts of the mouse x+y axis, usually thus in 1-2 directions. So for instance you'll be playing and out of nowhere your right and down mouse movements require a huge movement in order to move it even slightly, whereas the left and up and inbetween directions are perfectly responsive. It will last a few seconds then disappear, and re-appear randomly in different directions.
If like me you've lived through using classic old ball mice, it's a bit like when you used to get some lint or dust stuck in the mechanism, and the mouse ball would roll fine in one direction but immediately get stuck in another.
Edit: Wow. That actually worked for me. Maxing in-game sensitivity but lowering mouse sensitivity via the mouse's properties in Windows.
Maybe it does have something to do with modern gaming mice's higher DPIs, not sure. I'm using a Logitech G600 atm.