Maybe this can help: Game Cursor Constantly Breaking/Glitching/Switching Mode? - #2 by W4RP_G_CZ
"The problem is caused by a very hidden hotkey:
Settings: Hotkeys: Camera Navigation Hotkeys: “Move Camera With Mouse” unbind (so can’t be activated)
To be 100% save you can also Settings: Game: “Click Drag Panning Speed” to 0 (So the navigation via right click on mouse won’t work at all.
I personally use the navigation to send the cursor on the edge of the screen, but the navigation with arrow keys is also possible with this option."