Wrist Error?

Hey all. We have a Global Image 574 CMM. The head is a PH10M. The controller is a PHC 10-2. We use 2013 MR1.

A couple of weeks ago, we started getting wrist errors. It was obvious that the head had been crashed even though no one knew anything about it. It looked like a pretty good crash based on the gouges in the head. It was still able to run, we just had to deal with wrist errors popping up, and having to recalibrate, etc. It was a pain, but we couldn't afford to be down a machine. We had ordered a new head, but it was taking a while for Renishaw to get it to us. Once we got it in, we changed it out, and it was less than a day before we started running into the same issues/errors.

The issues are sporadic. we may not get a wrist error for like 5-6+ hours, but then we will get them back to back to back. We had Hexagon come out. Of course, it didn't want to error out. When it finally did give a wrist error, it shut off the PHC 10-2 controller and he said that since that had turned off, he couldn't see what the issue was. He checked a few things, said that he couldn't find anything, and left. We had thought about ordering another head on the off chance that something was wrong with the rebuild. That has happened before. The machine ended up going all the way down because of an air leak. They came back out to fix and replace hoses.

He got it back up and running. We were running it. It had a movement interrupted or some error. Totally correct and explainable. I pulled it away and restarted the program. It went to change angles and there was a thud and then a wrist error. We got it going again. We tried to recreate it. Finally, it did it again. He popped off the cover and checked everything out. He found that the belt for the Z drive had a chunk out. Everything else he checked looked good. We ordered a belt. He thinks that will fix the problem.

I wanted to bring this before the group to see if anyone had any ideas. I might be wrong, but I'm not necessarily sold that the belt for the Z drive is causing the issues we are having. I also don't necessarily think that it's the head. These wrist errors seem unusual. Here are something that we have noticed:

1. Before whenever we have ever gotten wrist errors, the wrist goes completely limp. This time, the wrist locks into a funny position.
   
2. I think that a good majority of the errors occur when it is in the process of changing angles or after it just changed tips and it goes to the home position and unlocks and relocks the head. The program will tell it to do A0B0, but it will go to like just off A0B0. It can be off in either off in A or B or both but it will think that it is at A0B0. Once you clear out the error, it won't reset to the correct angle, but if you tell it to go to A0B0, it will usually reset. Sometimes you have to turn it all the way down and bring it back up.
   
3. Sometimes when we get the error, we can clear it and keep going (if it didn't go to a funny error), all is ok. Sometimes, it will show a shift in the Y axis results. When we see the shift, it is always in the Y axis.
   

These wrist errors just seem out of the norm from any that we have ever gotten. I'm just concerned that there is something else wrong and after they change the belt, we still going to have issues.

Any thoughts or help is appreciated. Thanks.