My best guess is taht Marantz Changed something in DLNA Communications so that Heos app can easily be usedTheEmpathicEar wrote: ↑Sun Apr 30, 2023 3:02 pm Why were you able to connect to your Marantz receiver w/o HEOS?

The best would be to Generate MMA LOG id and also Generate MM5 LOG ID on same track so that Ludek and Michal can compare Packets communication and figure out "why and what is eating our chickens, if it is not a wolf".
EDIT: Marantz NA-11S1 is certified to be DLNA Renderer so it is possible that also have a say in compatibility.