Hi Andrew and Noel96, downloading and re-installing the https://www.pgmusic.com/support_macintoshupdates.htm update
seems to have fixed it. (I had previously installed this update but re-installing it appears to have rectified the issue. (I have no clue to what may have caused this problem)

I was able to enter instrument and dynamic changes via Bar Settings and save the SGU file out, close BIAB and when re-opening the prior changes were saved and all correct.

So (for now) I believe the issue to be resolved thank you!

I do have one other query which I have not been able to find in the manual .... when implementing "pushes and holds" in a chord chart that has chorus repeats, how do I set the pushes and holds to occur on the repeat and not on the 1st time through? (or vice-versa)??

I understand it's possible to do this but have no idea how to make pushes\holds play one time and not on the repeat chorus..

Many thanks,
Gary.