There was a lovely change in design that is almost never used anymore.
Notice that people first move the frame, THEN move the motor?
instead
1. Pulse frame motor(A) to move frame motor (B) into position where it WILL contact a not gate. Same pulse fires the redstone frubes to get the blockbreakers.
2. Takes 16 ticks for that frame motor (b) to finish moving. On the 17th tick the notgate is still on. It will activate and slide the entire frame forward. Gravity blocks have not normally started to fall, and your frame is already moving forward.
This bore moves so fast, nothing stops it.