Cant skip party of an offline track :(

[beastmovez]

Hey guys,

first time posting here, so sorry if its the wrong forum or some wrong formation. Now my problem:

I love the fact that I can add audiobooks from my PC in my spotify acc. and download it on my android to listen to it offline. Now, since 2 weeks or so, I cant skip to the middle of an Audiobook (for example). The Audiobooks are one massive MP3 with a length of like 900 Minutes. Now lets say I listen to the first 2 hours one night. Why cant I skip to that exact point later? I swear it was working 2 weeks ago and I dont really see a reason why it shouldnt, but for some reason it does. It starts from the very beginning and if I click on the timeline it just jumps back to the start.

Can you help me or redirect me to the right place/forum?

Thanks and greetings