I have a QLG1 that I have to run with GPS check = 0 on the U3S. Tried it on a QCX just the other day and it worked just fine. The NMEA data was parsed when the GPS got a satellite lock (3D fix IIRC). The frequency calibration routine relies on the PPS signal and this worked flawlessly, just takes ~5s to run.
Daniel Ekman SA2KNG