Interference

[VA561]

I have a 1960 rca color tv. I use the dvd player through an rf converter to play color programs. It is the same rca brand converter that I use when I play dvds on my 1950 Philco. Here is the problem that I am having. When I play shows on the dvd player, whether they are 30 minutes or an hour, everything works fine. When I attempt to play a movie I get some sort of interference as indicated by the picture. It only seems to happen when I play movies and it does't matter if they are old or new films.
This only happens on my color tv. not on my black & white Philco. It doesn't make any sense. I switched dvd players and switched from channel 3 to 4. The interference will stay there for about 4 seconds, then disappear for about 2 seconds and repeat the cycle over and over again. Any ideas would be greatly appreciated.