I was clutching at straw about cleaning the tape, always worth asking. I don’t mix tapes, I have only ever used sony tapes same as the camcorder.
I think that your right and I need to get it looked at, which I’m looking into now. I have recorded onto a new tape and replayed and all is fine, but pervious tapes have this pixelation line. So think your completely right about the alignment of the heads and have them properly cleaned.
Thanks for your he in this matter, will let you know how I get on