Thanks for responding Noel.

I should have clarified that after I discovered the issue in Stylepicker, all subsequent searches were in RT picker, but I filtered by RT number.

Your suggestion of filtering by Set number showed me that I had wrongly assumed that the Bass, Acoustic, Jazz Sw 110 folder contained all variations of Sw 110, same for Sw140 & Sw190.

The relevant folders were not in my BIAB 2018 but were in BIAB 2017 on my desktop, so I copied and pasted, rebooted and Rebuilt RTs. Now all present and correct.

However this is just a quick fix, it doesn't answer the 'What Happened' question and I am reluctant to update 2017 on my desktop.

I will contact PG support and refer them to this thread.

Regards
Vintage