Hurray, that was indeed the problem, together with getting diverted by ATC (go around calls) which doesn’t make it a direct flight anymore (I guess).
It worked for me with this flight, from Nice to Bordeaux
I set the destination to parking spot 26, easy to find
The weather cooperated to give me a straight in approach on ILS runway 29, while approaching at 280 degrees from Nice, easy.
Direct as direct can be
I filed an IFR request with ground 118.7 (request IFR clearance for Instrument FP) after booting up the plane (didn’t touch anything on the checklist, just referenced it to make sure not to miss any steps but did not tick anything or use the look at icon)
ATC send me to 18K ft and left me there all the way, just a couple hand offs to acknowledge while enjoying the terrain below and other traffic in the sky. It had one small quirk where it briefly told me to climb back to 18K ft on approach (after earlier telling me to descend to 4K ft) I acknowledged, started a slow climb and it soon corrected itself to directed me to 3,000ft, max 220 knots, then handed me off to the tower for landing clearance.
Easy landing, turned off the runway and asked for taxi to parking. The crew were waiting for me at the spot I had picked beforehand. I followed the directions of baton guy, then shut down the plane according to the checklist. (Not ticking anything, just looking at it)
That did it, achievement unlocked. No need for AI pilot