Mouse input erratic when connected remotely

Remotely controlling the Minecraft client results in erratic mouse movement. (Spinning erratically while looking directly up.) This can easily be duplicated by testing with RDC.

I use Kavoom to control a second account running on a second machine, giving me seamless use of a single mouse and keyboard between two computers. This has worked flawlessly through version 1.12.2. However, now I am now unable to control movement in the snapshot versions on the second machine. The mouse works normally in menus, but not when controlling the character.