I have only noticed that it does this with modest. Every other one mutes it. Muting it is very difficult right now though, since hitting the icon where it shows the current volume is so small and I have no stylus (haven't had one for ages)
And turning offline mode vs turning the wifi module do the same thing, but since wifi is off, there is no point in having the module in memory still (I hope I'm using the correct terms!)
Flight mode has wifi off
green button vs grey button is about 3 or 4MB, I'll take whatever MB I can get.
I've also noticed bluetooth is a bit confusing. I have to turn the module on, then press bluetooth to get it to show up.