Thanks for that. I am suspecting some problem in the re-assembly. It works fine until the cover goes on. This will bring up the shaft ends to the proper position and perhaps revealing the misassembly when the slack is taken up.
I've cracked the box twice more since to try and pin it down.
The manual is also vague about the order of re-assembly.. there are a few return spring dohickeys with secondary spring-loaded ball bearings that can go pearshaped if put in out of order. All this ... and then the hoiking up onto the clutch!! argh!!