most the time from what I have seen is that the solder connection on the internal board brakes which causes this problem. I have seen this type of problem come up alot surrounding these type of connections due from the stress of twisting the cable on and off. I am not a TV repair person but I have many years of componet level repair experience.

Easy way to test this theory is hook up your TV and flex the cable connection to see if the signal comes in and out.

oh yeah I dont recommend taking your tv apart..... lot of stored voltage that can stray easily..