That is strange, but no problem on my end. I think there some issue on your tablet side. Since your mouse work as normal so it not really Groupy issue. Please check if your pen/tablet drive have compatibility issue with Groupy. I am using those cheap Huion Inspiroy H640P and have no issue with it.
I have forwarded your questions/problems to the Stardock Support team for their futher assistance or comments . Please keep an eye on this thread for any updates. We appreciate you feedback and patience.
Thank You,
Basj
Stardock Community Assistant.