I've got this again after installing the latest version... Before everything synced fine but afterwards no more. Even the "workaround" with initiating sync on Android doesn't work (or I'm doing it wrong... And it has been my own advice at some point 
Never ending synchro - #19 by 3ter)
UPDATE: Finally! I played around a bit more, starting sync on Android, starting Joplin on Desktop then starting sync manually on Android again and jackpot!
And every sync afterwards works like a charm again!
