Hey Berty,
I just posted a thread about the same issue... Didn´t see your thread until now.
I´m having the same problem... it fastforwards, stops then it resumes. I have done several things and still the same issue (unpair, pair againg. restart my phone, download different songs). Hopefully someone can help us both.
What I havent tried is turn off mobile data on my phone... Maybe all msgs from whatssap breaks the signal or something