Podcasts via Airplay to Airport Express pause volume change

I have a strange issue I can't seem to get to the bottom of

I have an AirportExpress connected via ethernet, wireless turned off and an Aux cable to a speaker

When I connect my phone via Airplay to the AE and go to the podcast app the starting volume seems to be about 20%

If I play a podcast and increase the volume all is fine

However if I pause it from the lock screen, when I re-start it again the volume goes back to about 20%

It doesn't always do it but it does it most of the time

If I try other apps like apple music or spotify then these don't seem to do it

Has anyone else seen anything like this?

iOS 18.2.1 AE 7.8.1

Thanks