Various things to try:
Test all upper carriage Limit-Switches with a multimeter. If they all register without any trouble, then make sure they are being depressed fully when the carriage fully extends.
If pully system... check to make sure that belt isnt slipping. When rubber gets old... and or dirty, it loses its grip and or elasticity. Use rubber cleaner / re-new.. or at least rubbing alcohol, to clean the belts and pullys.
Check the PCB for any loose connections / connectors. Pull the relays if they come up... then re-seat (with game off).
Check all connectors for any blackened areas, and or loose / bad pin connections... where a short may have taken place.
Check PCB for any capacitors that are bulging at the top, possibly leaking. Also, Sniff the board to see if you detect any smoky smells from burnt electronics.
If relays pop out, try swapping them around with the others.
Check actual games microswitches to make sure they work well.. and are not shorted out from some soda spill.
Check for loose soldier joints.. soldier than looks more grayish than shinny. Re-Heat and reflow the areas as needed.
You could also check the power supply, for proper voltages. Many power supplies can be cranked up a little if they have fallen under voltages. If possible, Disconnect boards before attempting to turn up the voltage pot.. as you could accidentally fry them.
Most crane issues are either mechanical, or they are connector related.