Installed Marvin French doors with side panels in 2012-13. It has an integrated multipoint locking system. The lock recently failed but is still under warranty, so Marvin sent me a replacement unit. However the thumb latch on the replacement lock is very difficult to turn -- I can barely turn it using all of my strength and my wife has no chance of turning it. There is a night and day difference between the thumb latch operation of the original (now failed) lock and the replacement unit. Marvin service is throwing up their hands and ignoring the possibility the replacement unit is simply defective. Does anyone have any experience with this problem?