Need help/advice/opinion

Hello. I'm from Lithuania. So I apologize, because I write a lot with google translate.

We bought a Jaguar xf, 2009, 3.0 petrol. 175kW.

Everything was great for 6 months, but recently there has been a problem that it throws out of gear. When starting to move in "R" for about 1 meter, "P" switches on with a crack. The selector indicator remains "R", only it flashes. Then you need to switch to "N" or "P" to be able to move. If you start from "D", also after moving a little, "D" starts flashing and you find yourself in "N". The revs can be raised, but the car stands still. This is not an everyday problem, sometimes we can drive without problems for a whole week, and sometimes I can't move from the yard. I have scanned errors with LAUNCH and got the code U0405-8f invalid data received from speed control module. I checked the abs sensors and I sometimes get all these problems while standing. I'll explain, I start the car, turn on "R" and don't move anywhere, after 15-20 seconds with a click "R" flashes, and it feels like the box has switched to "P"

Thanks for your thoughts, guesses and advice.

Forgive me if any of the expressions are incorrect. Age is no longer the same as learning :)