Why do I have to wiggle the S-video cord to get color on my TV?

Actually, it's my brother in-law's TV. He has a Panasonic TV that is only a couple of years old. And if he wants to watch a movie on his DVD player, he has to slightly pull out the s-video cord that is connected to the back of his TV to get color. He has to wiggle the cord in and out until it is in color. Then when he shuts the DVD off, and wants to watch cable TV, the TV is in black and white. He then has to go behind the TV again and wiggle the s-video cord in a little bit until he gets color. Upon several visits to his house, I realized what a pain this is.

This is the deal. His connections are as follows:(best I can remember, but I did diagram his whole set up on paper, which is not in front of me now), He has a cable box for regular (not digital) cable, DVD player with s-video cable connected directly to s-video of TV, a VCR, a stereo receiver, a cassette tape player, and a CD player. From what I've seen, his connections seem OK.

My brother in-law bought a new s-video cable and still has the same problem. I spoke with a guy at Radio Shack and he said that the s-video cable was probably of poor quality. So I bought the Gold Series s-video cable, installed it and still have the black and white problem. I don't get it.

Last thing I looked at was the female s-video connection behind the Panasonic TV and it seemed fairly solid, but I felt a little play when plugging in the male s-video. Does that part of the TV need servicing. Maybe a re-solder job?

Here is the other thing. My friend at work told me he had a black and white problem with his TV and he took the back off and resoldered that female s-video connector and ended up not being able to get any picture at all. Found out from an electrician at work that he should have used a low voltage soldering iron instead. He ended up having to buy a new TV.

Can anyone help me?