Why Qobuz browsing resets every time the Lumin app is set in the foreground ?

[simbun]

Firstly, I assume you're talking about the app updating its cache of the MinimServer library rather than causing MinimServer to perform a rescan itself.

I've only used it very occasionaly, but on Android a rebuild/update needs to be specifically requested, so I'm surprised that it's happening automatically at all.
Have you tried uninstalling then reinstalling and just setting up MinimServer to see if the problem persists? Likewise, just installing Qobuz to see if browsing is reset every time?