When PSP freezes, swipe in from the right side of your tablet. A "swipe" is similar to swiping a book in order to turn the page. It may take several tries, but eventually, you will get a Windows menu to slide in from the right. Touch "Settings" from the Menu Options and then find the Power Icon (it looks like a circle with a vertical line on top). Touch the Power Icon and choose the "Restart" option.
After the tablet restarts and Pro-Stitcher launches, from the main Pro-Stitcher Screen, go to File > Shutdown > Reboot. After these two reboots, the tablet should have fewer freezes.
As you continue quilting, please try to look for any constant that occurs prior to the tablet freezing. If you continue to have problems, that information may help your technician to troubleshoot further.