Can a faulty XLR mic cause the video to jitter in low light filming even on Manual focus and iris.

Unlikely. What are your WB, Shutter, Steadyshot and FLICKR REDUCE settings? What is your light source?

Manual WB, shutter 60, tried steadyshot on and off but i did have flicker reduce on. Gain db6. The lighting was very poor but it happened at a dance show and lighting was fairly well. it seem to happen with heavy bass noise beat.

And this is on tape playback, or only in the LCD while you are shooting?

Heavy bass noise causes the problem? Sounds like it was affecting your steady shot. Was it on?

Saw it in the screen and on the tape.

Heavy bass noise causes the problem? Sounds like it was affecting your steady shot. Was it on?

I tried it with it on and off

Is the jittering in time with the beat?

Yes it is in time with the beat. Camera was plugged into main at both venues

Can you post the video with audio so we can see what your jitter looks like?

Then I think the vibration from the beat is indeed affecting the Steadyshot. Remember, it's a moving element whether the OIS is on or off. I think the bass is shaking it.

But that's just a guess.

Well I have ordered a replacement mic as the sony one is rubbish. I hope it is just that. Its fine when I film sport on it and that is the bulk of my work. I really want a NX5 but that will have to wait until i have £3500 :(

Can a faulty XLR mic cause the video to jitter in low light filming even on Manual focus and iris.

Very highly unlikely. The two circuits don't really have anything to do with each other.