Looks like you’ve got a problem with resources not being released which is resulting in responses to strokes getting slower and slower.
I had a bit of a play yesterday and today and it appears to be when you leave skritter and do other things (Chrome, FB, etc) then come back to it. I did about 70 cards (obviously only some of them writing) without any issue apparent. Once I leave skritter and come back to it there’s a noticeable difference. If I do it a second and third time it becomes as good as unusable. A force stop and restart fixes it.