Based on your message, it looks like it's an internet issue.
By the way, what's your operating system version?
That sounds strange.. hmmm
Have you checked if you have an updated version of Spotify through the Google Playstore?
Also, Wlan and 4G have differences when it comes to signal, so it could be that one is faster than the other.
But nonetheless, I'd suggest you to contact Spotify directly through their Contact form, so they can provide you the best resolution about this issue.
You may also reach them through their twitter account @SpotifyCares, or through their Facebook page.
Hope it helps.
P.S. I'm not a Spotify employee
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