Thank you rharv for your detailed reply. This is exactly what I was looking for and clearly there is an issue from my end.

When I first started to get these problems I looked for a RealBand update (I'm embarrassed to say that I don't even know what 'build' my version is or even where to find it).
I thought it might have been part of the BIAB update, which I did download and apply but there was no reference to RealBand there.

Thanks again

John