I've never heard of that problem. I suppose you should be able to isolate whether the cable changed (which is more likely) or if the camera input port has changed on your dashcam.
If I were you, I'd call Blackvue tech support. Or you could send an email to cs@pittasoft.com. Calling will probably get you a quicker answer, however phone support is closed on Sunday and since S. Korea is a day ahead of us, emailing might be just as fast. - - Good luck.
I drove the car down to the guy who installed the camera in the first place. It took him less than 30 seconds to fix the problem. He took a look at the end of the coaxial cable from the rear camera, said, "It's broken," pushed it a little bit and shoved it right in. Everything works fine now.