"Downloaded" song not actually downloaded

[collectionpoint]

Sorry if this has been asked before - I did try and find a post with the same problem in but none were quite like this.

So I'm downloading a huge playlist for offline availability - then occasionally it will zip through the downloading and download at an incredibly unlikely speed. The songs are marked as downloaded (i.e. green down arrow).

However when I'm in an area of low data signal many of these songs struggle to start as if I am trying to stream them.

I don't really know how to get them downloaded legitimately because, of course, Spotify thinks they're already downloaded and so won't try to do it again.

Has anyone ellse had this?