To add to my comments above … I made a test flight yesterday between KBUR and KLAS using both GSX and PACX. There was no obvious conflict, though of course there is no explicit coordination between the two for stuff like loading/embarking passengers. So in my case, GSX actually finished sooner than PACX “thought” pax loading should take. I used PACX’s interface to request expedited boarding and a couple minutes later, PACX said the cabin was ready for departure.
Everything worked fine through climb, cruise and descent, but for whatever reason, PACX didn’t recognize the landing at KLAS. The progress bar in the display stopped at touchdown (we were a couple minutes early) but never triggered the landing. Even after sitting taxiway for a couple minutes while waiting for GSX to send a follow-me car to the gate, the arrival audio never played and PACX didn’t recognize completion of the flight. I’ll repeat the flight at some point this week and see if the issue recurs.