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?