Hi Dean,
You may find the issue is still the #3 switch, because even though it works ok, the transfer time between the contacts may be too long.
For the search unit removal. Remove the power, then the comb edge connector from the search unit. Now remove the 3 large bolts in each corner of the search unit. Leave the last one in and steady it as you pull forwards. It will come off easily. Now you will see the stopping switch assembly. Only one of the switches on here is the stopping switch. Remove the circlip and pull forward. It will come off. Check the switches on the bench and check their connectivity on the wiper circuit on the rear. Clean the wiper tracks and clean the wiper contacts (these are still in the jukebox). Check dry joints where the wires from the stop switch is attached to the wiper track.
When done set the carousel so that U0 (I think it's U0 but will clarify later) is at the top. Now slide the stopping switch assembly back on and line up the words 200 to the 3 o'clock position where there is a bit of a ledge in the mounting bracket. Also make sure you wind the record playing annunciator round to show U0 also).
Re fit search unit and bolt up. Don't mess with anything on that unit as it has nothing to do with your problem. Connect the comb edge connector and select a record. Try all selections like A1,B2,C3,D4 so you have covered all letters and numbers. If the search unit spins forever on a certain letter or number then it's a poor connection on that comb contact.
Hope that helps to get you going ,
Nigel, uk