Hello Again.,
well I spoke too soon.

The "return to factory settings" seemed to help although it's been short-lived. After returning to factory settings and making my required changes to instruments via "Bar Settings" it initially worked ... (i.e. I was able to close down the program and re-open it later on to pick up where I left off).

THEN .. an hour later I opened BIAB to complete the same file and all previous changes made via Bar Settings were COMPLETELY GONE AGAIN! (arrangement window has remained the same but all changes to individual measures via bar settings have been removed to nothing!

This is a big issue for me as I find no new arrangement file works satisfactorily without making at least some modifications to instruments via Bar Settings option.

Now at a complete loss.