DFN problem with Lancia Musa

hello; I drive a lancia musa with dfn transmission. problem: the dfn switches “from time to time” to “N”. “from time to time” means that he does it in the morning hours (temperature) when braking after approx. 5 minutes; never on normal journeys with overland journeys e.g.. the musa is then sometimes 20 minutes (sometimes only 2-3 minutes), motor runs normal, only it is impossible to take a walk. by repeatedly setting off the motor, then at some point again a walk takes place. today e.g. he went to “N” and it was immediately put in over + one walk. we were already in two workshops. the “seller” was changed, the clutch changed and of course several times read fault memory, as well as new software was played up. it also happens that the musa 3 – 4 days without problems, until he shows again the same problem. the fusssssrat are not able to turn to me directly.