We've discovered that not all couplers are made alike.

With two drill motors installed we noticed that one had a slight
wobble. After some close inspection we noticed that the coupler that screws onto the drill shaft was defective.
The peice was not drilled in the center. This caused the
deflection on the end of the transmission shaft.
We called a team down the road and got their two couplers
(Thanks Team 188 - Blizzard!). Back at home base we
screwed these in and while they're better, they're still not perfect.
So now we've got 3 and all of them a different. I put in the best one and spun up the motor. Its a lot better than before. In fact,
it'll have to do because I'm stuck with these cruddy couplers.
(I wish I used lovejoy couplers)

One one else experience this?

Ours wobble too. I think that FIRST drilled them wrong.

Same here. I should hope that that does not create a significant problem or anything.

I wonder what happened to our 2nd left-handed screw; it seems as though it never came in the kit. Had to get a replacement from MMH.