As you've surmised, the audio is completely separate and not relevant to picture issues with component signals. And, you should be seeing zero
random blue screens. It's not normal, indicates a problem somewhere, and you shouldn't have more than one of them at the beginning, or when switching sources, once your problem is dealt with.
It's more than likely a cable problem, IMHO. The projector is loosing sync (obviously), which is carried in the (Y) component cable, along with luminance information. The other two cables (Pb..blue & Pr
..red) carry color information only
. The machine can't 'hold sync' unless the sync signal is stable in the Y cable, so if it's flaky, for whatever reason, one can wind up with the problem you're seeing.
A simple way to see if it's the cable is to swap the connections around. Remember that all three cables are generally identical
, the difference is the color of the plugs on the ends.
Let's isolate the problem by trying another plug in the Y jack. (It's not necessary that the PJ be off when swapping input connections around, in case you're not aware. Far better to leave it on than to switch it off and on repeatedly.)
So, unplug all component connections on both ends. Then, plug either
the Pb or Pr
plug into the Y jacks (use the same color plug on both ends, of course). Leave the Pb and Pr
jacks empty. You should now have a glorious black-and-white picture
, assuming this cable isn't faulty also. Watch a while and see if the picture remains stable. If it does, you likely need a new component cable.