Sounds like a bit of Chinese engineering that couldn't pass an FCC or CE emissions test if it had to. Sorry to hear that.
I don't know your device, so don't know if it's a separate camera/video system or just a camera headed to an in-dash system.
You might try adding a substantial torroid (split 'snap' together style is easiest) on the lead to your dash cam to see if that is the source. Would try it out on the camera end first.
If that doesn't work, it could be the video end, if you've got a separate one, and you'd want to place it as close to that as possible.