Hi Guido, Thank you for presenting this mistake to me. Yesterday I uploaded the changeset with JOSM validator active. It flagged many mistakes which I had corrected one by one. Many mistakes were of poor mapping, not done by me. 
Today I corrected the two mistakes pointed out to you. Again JOSM flagged many other mistakes not made by me. I corrected them all. 
Today it took me 2 hours and 9 minutes to solve all the problems the JOSM validator showed. So this really is a valuable tool. nevertheless I was happy to correct this because now I improved a little bit of the Acapulco area on OSM. :-)
Thank you.