i have a device which can supports 4 cams to be connected to a dashcam and controlled by a remote switcher



the device works flawlessly capturing videos and switching between all cams but just one thing odd is the white banding lines it produced



some suggested me that to use something like picture below to eliminate interference but still no cure



just right before i'm giving up, i noticed something when i pulled out the power cable from the device just leaving some portion of it slightly inside the device, the white bandings vanished miraclely all of a sudden




but this didn't last long once i reinserted the cable deeper to fully into the device, the white bandings reappeared again.......

what could be possibly wrong happened here? or any solutions that you guys can be suggested for me to solve it? thx

checked but the joint soldering seems fine，still shiny and even， didn't notice any oxidation/rust as well, just some smudges around the joints(seems like intended)

i did test in my room with router power adaptor but the lines were not there, weird