Got the same problem now. Travelling with German passport SIN to MUC, only get seat confirmation, no boarding pass. Very annoying, because I‘m on QR0945 (departure at 2:00 am on Nov 6th) and actually did plan to be at Changi at around 9 pm to relax a bit after a long day in the city.
Are QR checkin counters really only open 3 hours before departure or is there a way to get airside as early as planned? Would it be possible to check in when the counters are open for QR0947 (departing 20:45 on Nov 5th)?