Forestidia sent me a video of their problem, here was my reply:
Hi, good video. This is a different issue than mobius's, but I know yours because I've already fixed it on Linux: Lix's cursor warps across half the Lix window.
Since no Windows user has reported the problem before, I kept the unfixed code for Windows because it looked cleaner. I should use the fixed code throughout and see if other people report problems.
-- Simon