It seems like "used" gets assigned the wrong value. https://github.com/PX4/PX4-GPSDrivers/blob/63990d218ec35ea965d634af6a79d3155561b743/src/ubx.cpp#L1723 it checks bit 0 of the flags when according to the [Interface Description](https://content.u-blox.com/sites/default/files/documents/u-blox-F9-HPG-1.32_InterfaceDescription_UBX-22008968.pdf) (page 150/151) it should be bit 3.