Hi, I've just tried again with a completely different project in Reaper and a different style with a different but similar result.
Using _Yazoo.sty (Yazoo River Pedal Steel ), put a push on beat 3 of 2nd bar with a hold, except drums - (^A...d).
The drums played through bar 2,(the rest of band pushed and held), then no more drums from bar 3 while rest of band continued.
So removed that push and tried another the same (^A...d) on beat 3 of 4th bar, Same result - band held, drums played through the bar then no drums from bar 5 on...same when I input a shot (^A..d)
Am I missing a critical part of this?

Thanks
Fats