Short answer. Excellent timing and looks like you have nailed it! All works.
Longer answer. Appreciate the efforts that go into maintaining / debugging something like this at all - let alone holding down the day job. I also took some time out as my Pi's headed off to the friend I was working on this for - albeit with piCore. Replacement Pi's turned up this week and today I got to do a clean Snake Oil install on them both (a 4 and 3B). I actually noticed the pulse suggestion on the installer page of the forum when checking I had the latest downloads and wondered whether I had missed it before! Anyway, I did the purge and all works as it should - on single Pi setup and on separate server and player Pi's, and on any combination of fixed or WiFi networks. Now feels rock solid.
Thanks for the effiorts. Still need to finish updating my install guide notes.
Gibbo