On Win 10…
In Key Editor I select a few MIDI notes and I use the mouse scroll wheel hovered over the tick value in ‘Length’ at the top of the edit window. When I move the scroll wheel the selected note lengths immediately go crazy, jumping to two quarter notes longer than they were and then any further attempts won’t let me reduce the note length at all.
When only one note is selected it seems to work fine.
Seems to be consistent.