Not being able to re-order Now Playing list (intermittent)

Android Phone App. Individual Premium plan.

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This has been happening on and off for a few weeks now.

Say, about 10% of the time, if i've got a playlist on Random, if I look in the Now Playing list there is no re-order option (no 3 lines on the right hand side to drag songs up or down).

90% of the time it's fine.. But I have no idea why this is happening.

It can the the same playlist - one day it's fine, the next it doesn't work.

Re-starting the app doesn't seem to 'fix' it. But, clearing the cache and re-starting the phone did... (but I dont want to have to do that ever time i hit this issue).

It's almost like, sometimes it doesn't think I have Premium... but I do.

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Anyone seen similar, or have any thoughts?

Many thanks