Since 0.26, the camera spins around erratically when trying to rotate with right-click after toggling confine to window.
And then the camera won't move when toggling lock while rotating while in-game. I also have vsync enabled.
Only real solution after toggling the options enough times, is to delete Loap.ini. Not sure why, and if this is a fullscreen related issue.
Fixed in commit eea54a6 (will be included in the next update, or you can build from source if you like).
It's purely related to the confine cursor option; fullscreen and vsync have nothing to do with it.