Ford Mondeo Mk4 2008 2.0 TDCI - Problem with starting after stalling in gear

Hello to all forum members!
For some time now I have been struggling with a problem that no one can solve.
Well, everything is fine with the car. It starts normally, it drives normally. But in the event that it goes out while reversing - as a result of adding too little gas or releasing the clutch faster - I cannot start the engine right away. You have to turn the starter for a long time, sometimes several times until it finally starts. Does anyone know what could be the reason?
Best wishes
Michael

The only thing you can do is go to the diagnostician's mechanic and force the fault, and then view the parameters during start-up.

Unfortunately, it will be checked at ASO in Slovenia, because it fell on a holiday trip ... I'm already afraid of the verdict and the price. Not to mention the repair time.

I was able to return this car to Poland.
At ASO in Slovenia, they found that air is getting into the fuel system. He was showing me and actually there were bubbles in the tube. The computer showed no errors - or so I was told. I wasn't there and I don't know if they connected it to the computer at all. They connected such a tube with a pear into the fuel circuit. They probably forced the fuel to flow by hand.
Without putting out the car with a soul on its shoulder, we set off for over 1000 km.
We'll see what the mechanic says.
I don't know, but if air in the fuel system was caused by leaks or a damaged fuel pump, I would also have problems on the road, e.g. with a drop in power, and if I idle, it could go out. Meanwhile, nothing like that happened. Everything works fine ... Just Enigma ...

Problem solved:
It turned out that the gasket was wrong when replacing the fuel filter. From here, air was sucked into the fuel system. After replacing the gasket as he took it off.