Well ... this is a new one for me. I was working on my bathtub swap out project, which included replacing the shower valve and temporarily moving a baseboard hot water heater. About 1/2 way through, I opened a new bag of copper crimp rings (Sharkbite Brand). All of a sudden, the rings did not want to go on the pipe and would not pass the 'Go' test. I went to the store and got a different brand (Aquadynamic) and the problem instantly resolved. Has anyone ever seen this before?