
If like me you've had enough of mouse scroll skipping in X11-based Desktop Linux Guest VMs, after years of searching I finally have the solution.
In all Linux distros with any X11-based desktop environment that I've ever used in VirtualBox as guest OSes I've experienced the same infuriating issue: if I were to scroll the mouse wheel slowly (especially when scrolling up-down-up-down...) — the inputs would randomly get "eaten" for some reason. This led to them not being registered, which was extremely annoying, because I had no clue why this was the case only with the Linux guests, and never with Windows XP/7/10 ones.