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Why is my clamp locking when I bring it all the way forward or back?

I have finished this project bar one detail, when I bring the arm mechanism all the way to the front of back it becomes locked and I have to press undo to get it back. I have been stumped on this one for a while. I have attached photos of the clamp below of it in it's starting position and then it in it's locked position. I will happily provide any extra information required. Thank you all in advance. New post this time with a link to the project.
Answers
The issue is caused by your Tangent mate that has Tangent propagation switched on. If instead you choose the longer arc face as one side of the tangent mate, and switch off the Tangent Propagation:
Finally, in order to limit the range of motion it might be best to specify Limits on Revolute 4