I m having a similar issue. QCT starts acting up several hours into a session. Will not advance in the panto mode. Seems to stick on the last zone, and the place the mark screen never comes up, goes directly to advance fabric to the mark. Ive closed the program, restarted, replaced the pattern and it still is doing it. Driving me crazy. And now i have to rip out the 4 inches that are out of whack i sewed before i gave up. This is only a large table runner not even a full sized quilt. I feel your pain!
deb