To prepare for playing from iPhone to be discontinued (and because the music kept skipping or interrupting when played from my phone, no matter what I did to try and fix it) I’ve transferred my music to a drive connected to my router. All goes well for a few days, then the Sonos app says the path is not valid. I have an app on my phone that enables me to see the folder structure on the drive and sure enough the music folder has disappeared (though all the others remain). I connect the drive into my laptop and everything is there, including music folder. Then back in the router and everything works for a couple of days until it doesn’t, and in exactly the same way. Any ideas?