Sorry to hear about your issues- sounds very frustrating, to say the least. I am a huge Canik fan, as well- especially their older metal framed pistols. Intermittent issues are the worst to diagnose.
A suggestion (guess) would be to check the metal rail inserts in the poly frame, give them a good wiggle with needle nose, without gouging/marring, to see if the rails have play or have worked loose. It would be very subtle movement. It could just be poly fatigue causing flex in frame.
Take some disassembly pics- sometimes a crack/issue can be spotted under magnification. Wear marks on rails can give telltale signs of alignment issue.
A suggestion (guess) would be to check the metal rail inserts in the poly frame, give them a good wiggle with needle nose, without gouging/marring, to see if the rails have play or have worked loose. It would be very subtle movement. It could just be poly fatigue causing flex in frame.
Take some disassembly pics- sometimes a crack/issue can be spotted under magnification. Wear marks on rails can give telltale signs of alignment issue.