Ok, New video track name was accidently renamed to an existing track name. See the Image attached. Not sure how it happened, but I would have thought if we are naming a new track, that if a name already exist it should error with a message. Not sure if this is a feature of SC though.
I only found out about this problem with i was adding a transparent track to the new timeline, and it was messing up, as the transparency was not coming through, and then realised that because the video track is named the same as the existing track, then it messes up with the new timeline.
This is not a bug. There is no requirement that names be unique as the names are not used internally. It does not cause a problem. They are for your own purpose.
then realised that because the video track is named the same as the existing track, then it messes up with the new timeline.
That is incorrect. You must have been confused by something else.