Premium account - downloaded songs don't play

[Ger21]

I've had a premium account with an iphone 7+ 128gb with plenty of space.  I've got about 1300 songs on a downloaded playlist (confirmed downloads) and more often than not, 2 out every 5 songs don't load or play...  they just stay at 0.00s instead of loading up.

I've re-downloaded, removed and re-installed the app, powered off the device...  not sure what else to try.

On a seperate note...  when I've re-downloaded, songs that were confirmed before are blanked out second time around.  What does this mean, the track has been removed from spotify?