Prismatic ray not scrolling correctly, tends to lock up

I have a prismatic ray that is not scrolling correctly when tuned into a very slow scroll with no sync. It jumps around, gets jerky, and even syncs. everything else works fine. I’ve been using it more for the hi-frequency synced stuff.

Very sorry to hear it. A few questions:
Do you have any issues with it when it is synced?
Is it possible that the sync switch is malfunctioning?
How old is the module?