I was quite shocked that the co-ordination between the two was terrible
Before you decide the problem is the "coordination" between GSX and JFK, you should first verify several other things:
Is your PMDG 777 configuration correct ? Are you using the native support for it that comes with GSX with the latest Live Update ? You can verify this if all your doors are named with the PMDG-specific names ( Example "Cargo FWD", not "Cargo 1" ) and their status is correctly recognized.
If it's not, perhaps your problem is your 777 configuration file which is wrong (either edited, created or downloaded before we added native support for the 777), and must be removed. You can do this by selecting the "Reset" option of the GSX Aircraft configuration menu, and being sure there's no GSX.CFG file in the Simobject\Airplanes\PMDG 777 folder too.
Service vehicles were driving through the aircraft and also through other objects on the ground
They surely don't but, before deciding it's a GSX problem, you should also check the AFCAD used by GSX is the correct one. You can do this by selecting the "Customize this parking position" from the GSX menu. The scenery editor dialog will display the name of the AFCAD in use. Check is the FSDT one, the one in the FSX\fsdreamteam\KJFK\scenery folder.
Is this a known issue and can it be fixed ?
Nobody has reported this before but, if you are sure that BOTH the Airplane configuration is correct AND the AFCAD in use at JFK is the FSDT one, we can verify this but, as explained in many other threads about GSX bug reports, ALWAYS include ALL the following information:
- The airplane used (ok, the PMDG 777)
- The scenery used (ok, FSDT JFK, but please check if the correct AFCAD is in use)
- The GATE used
- The GSX operation you selected (boarding, deboarding, catering, etc.)