Sony Super Beta SL-HFT7 video line out not working

Hi I have a Sony Super Beta SL-HFT7 Betamax which was playing fine
when suddenly the picture disappeared. The audio remained fine. I
was using the RCA line out cables when this happened. Then I tried
using the RF Coaxial out, everything worked fine (video and audio).
I looked at the circuit board where the RCA inputs are located and
everything looked fine. Does anybody have a clue what happened? I
prefer using the Line Outs rather than Coaxial.

Thanks.