I was so amazed of the new function and I'm testing it.
I think there's a problem with your algorithm when you save the array matrix into ram.
The bigger you set the finger pad the most ram it uses.
I'm using the windows developer preview but i'm almost sure this will happen on all O.S.

I made some tests and i figured out that you keep track of too many coords during the fingerpad press function. I think you made this to simulate the movement of the finger.

I thought about a solution too:
use a timer to read the coords and send the servos to the new coords or if you want to simulate the finger movement increase the timer loop so it won't save too many coords