It was the gun. After sending it to CZ-USA the third time, the gunsmith said he found a defect. In his opinion it was there from day one, just not easily diagnosed. He said normally they would replace the pistol a new one, but could not because the .40 was discontinued. He gave me three options: 1) try to fix my .40, 2) replace with a TSO 9mm (not an option for me because I was using it in USPSA Limited Division), or 3) refund. I chose refund.
Prior to this I purchased a STI DVC Open to shoot USPSA Open Division. It's a great pistol, but today I would have made a different choice. Considering that STI discontinued the DVC Open with no replacement and the phenomenal service I received from CZ-USA I would go with the Czechmate. Also, CZ-USA is starting to manufacture in the US makes them a top choice for me.