Thx everybody. I'm on my way from Brussels to far west Brittany to enjoy a month of vacations in wild nature with family. I will use this opportunity to explore the door and understand bits and pieces. Eventual fix and repair will take place when back to civilisation! Hopefully the issue does not worsen. It's a delight to ride the car (first real long trip)

 

Enjoy your journey, Serge!
Hope the CAT lives up to expectation and BEYOND, She's a Jaguar, after-all!
Regards, et Bon Chance, Ami, Stu

 

Update concerning my door opening, and good news!
It works now
I didn't come back on this thread because actually I didn't do anything and was planning to have the issue sorted out by my Indy this month (didn't dare engaging myself in the dismantling of the door panel and looking around in that mechanic/electric stuff).
I discovered that it had recovered by chance, because yesterday an issue that had come coincidentally at the same time with my passenger side mirror (tilting too much downwards when starting the car and/or rear gearing and not coming back rightly) had surprisingly disappeared. Today I therefore tried to open my driver's door (usually I entered into the car using the passenger door) and tada!!! it worked!
So both issues disappeared at the same time while they were there since 6 months! Bizarre, bizarre, the X350 remains a strange beast with its electrical gremlins...I hope they will not come back!
Could the issues have been related to humidity or bad electrical contacts that would have "dried" now? or an electronic bug that vanished during repeated switchings?
Anyway, I'm relieved and happy now, I saved some bucks not being obliged to have it checked/repaired and the counter that should not go beyond three issues at the time has just gone down to one (some ticking/clattering at cold start which is still around). I can live with that and enjoy my cat
Serge