Parking in the one-way street

Hello to all traffic experts, look at the pictures , maybe you can recognize a traffic violation there which I oversee. Following facts, my boy has parked there (white Skoda) and has received for it a ” communication to determine an irregularity “. What is now exactly accused to him he gets later from the penalty office. I can find nothing, especially since I park there myself from time to time . It is a one-way road , and there may be according to StVO § 12 para. 4 l As far as there are rails on the right side as well as in one-way roads (sign 220) may be kept on the left and parked. The loading zone, which is not marked, is also not hindered. Also, the sign stop ban sign 283 does not hang parallel to the roadway, so it has no validity for this side. On the right side it hangs correctly. There is also enough distance to a junction or estuary available so it can not be. d on the sidewalk it also does not park, none of the wheels touches it even slightly.Perhaps it can lie at the sign 325 “Start of a traffic-free area”, because there must not be parked outside the marked areas.Parking is prohibited outside of the marked areas, except for boarding or discharging. But first there are no marked areas there, and secondly it is on the right side of the road. hnseite nevertheless also properly marked with the sign 283 under sign 325. That one could have given itself in this case also because the traffic-free area is also valid there. So how do you see this ? I recognize nothing for my part and think once here the lady from the office was a bit hasty and wanted to bring a few silver pieces to the city treasury in the sag. But I gladly let myself be taught a better one. gruß gispi97