A follow up : contrary to what I wrote juste above I get this error message when starting P3D only at LFPO. I quit doing anything at LFPO pending resolution of this constant GSX crash now.
In between time I wanted to see if I could still continue to customize airport, and I went to FMEE to try customizing a parking with jetways, as they apparently don't work now with P3D5.3 pending a HF (was already the case with 5.2 and it was solved by a HF but now appear again with 5.3 wff ?)
After playing with the parking customization, specifically correcting the stop distance and various equipment location, I clicked the don't display jetway as the one from the scenery still show. If I do not click this Don't display jetway I have two jetways displaying, the one from the scenery and the new one created by GSX.
The one from the scenery do not work with Ctl-J (not sure this was how they were supposed to work) but in GSX I got the message that the jetway can't work (or something like that) - Now I want to replace the original jetway with the GSX jetway, and see if it works (I had just done that at LFPO anf found one jetway model that would work (num 5 to test) but I am stuck again because GSX now crash everytime I start at this parking place.
I customized the stop distance but when I use the warp me there method the plane is well forward from that stop, and anything I do GSX is now crashing also.
So now GSX is crashing both at LFPO and FMEE - luckily I was able to customize a parking spot at LSGG (from FSDT :-) but I have to sy that the jetway was working good since the beginning.