No error codes? What does the analyser report for encoder counts for the steer wheel encoder ECR4 A2.1.10 (should increase/decrease smoothly), the lift pot POT4 A2.2.9 (10v full raise, 1.3v full lower)?

Then check A2.2.10 the actual lift motor speed and A2.2.11 the lift motor target speed? Also A2.3.4 the lift motor current?

It sounds like a poor connection to Access 2 if its not coding, looking at the wiring diagram, ECR4 and POT4 share some common connections, CA404 at Access 2, pin 4 is shared negative and pin 3 seems to be a shared positive.

My inclination would be to unplug CA404 from Access 2, turn it over and check the sockets in the connector. I usually do this with a spare pin, just pushing it into each socket and checking its not loose - I've had two units where this has caused the most bizarre issues.