It seems that after the 7.2 update , even with the Workaround (restart ES over web-ui) Moonlight doesnt work anymore.
The initial Problem was mentioned in this closed Article:
https://forum.recalbox.com/topic/21446/moonlight-on-recalbox-7-behave-strange?_=1619249007033
I didnt tried a complete reinstall yet. I will test this soon.