Multicast not working via wireless

Thanks IIeachii, your linked threads gives me some hints to investigate further, unfortunately I didn't find that thread before, I only found this similar one, which didn't give me a real clue

I've got it working now, I omitted the forward-rule in the firewall that already is set by the igmpproxy start-script. Unfortunatly I have, like already predicted, horrible stutter, so it's unusable.
My next approach is, as udpxy works perfect, to send the stream via wireless-unicast to the repeater-device (OrangePI), and convert it there back to multicast and also prepare the request for udpxy, so it's transparent to the media-receiver. My question: Is there some SW opposite udpxy?