I had the same issue. When i got home from a drive i checked the level in netural.

I suggest doing a service on it. Its piss easy.

Take the cover off. Take the filer out, new filter in and cover back on.

Top it up with oil..

Start eh car up. Check level.

Top up again.

Put it throung the gears when in the drive...

SO P for a bit then R then N and so on. Leave it in each for about 10 seconds.

Make sure the fluid level is all good.

If s**t keeps happening then go to a trans joint or someone that will read the diagnostics off it for ya. It may turn out to be a solinoid and if so its easy to replace your self. Its just the same as a oil change BUT you need a torx to undo a screw and u unclip it, new one in and fix it all up again.

Other wise it may be a whole new trans for you...Just check the magnet inside the trans when servicing it. I had a fine powder in mine from the bloody mesh in the solinoid and that screwed me over.

PM me if ya need a hand or something.