Or should I say, this particular coupler from China isn't meant to handle so much stress.
We have been trying to dampen some of the vibration caused by a huge lead screw that we use to raise and lower our ball holder. Mounting with grommets and the like helped some, but still the vibration was intense and the noise was horrendous. So I had the bright idea to get some Helical Couplers and see if they couldn't absorb some of the movement.
Unfortunately, I was wrong:
https://drive.google.com/file/d/0B5a...it?usp=sharing