I received a call from the owner of one of my recent slave-clock quartz conversions, that it was running slow and occasionally stopped!
Back in the workshop I noticed that the counter-weight portion of the hands were extremely close at certain positions, and my guess is that they had been touching. The hands had small additional weights riveted to them which increased their thickness, so since I used a high torque movement I removed the weights and the clock has been running fine for several days.