iPhone plays music that isn't on the device. How?...Is it not on wifi or data.

Apple Music

Confuses the heck out of me….

iPhone 5s contains some of my purchased music, downloaded directly from store onto the device and some of my ripped cd’s sync’d from Mac to iPhone via iTunes.

When I want to play music - I always choose the “Downloaded Music” option, confirmed by the little message confirmation display which says, “Showing only music on this iPhone”. Most often, I’ll choose “Songs & Shuffle”.

I have 3 issues:

1) How when the device isn't connected to wifi or data, Does it randomly play purchased music that isn’t on the device. Sometimes it’s just the occasional track, other times it’s like every 3rd or 4th track and several tracks in a row.

2) Sometimes a track will end and then there's just silence, a quick look at the screen and it displays the artwork for a track that isn't on the device, then after a few seconds it will move on and display & play another track, or just silence again when the track isn't on the device.

3) Sometimes it's a mix of both 1&2 behaviours

I don’t have Apple Music subscription or use iCloud library.

In an attempt to find a resolution, I’ve already done the following:

- reset the iPhone

- deleted all music from the device

- downloaded music again directly to device

- resync’d only ripped content via iTunes

Yet still the thing will randomly (or not, but just attempt to play) play music that ain't on the device. It's been going on for ages through at least 3 iOS versions, but seems to be more frequent since iOS11.

That Sony NW-WM1A player is looking more and more attractive.

Any advice appreciated.