Orbi RBR20 IGMP proxy behavior

Hi

I've been now debugging my IPTV device problems on Orbi for quite some time, with couple of past firmware versions without any clear difference.

Now how it seems to me, is that the IGMP proxy doesn't somehow behave properly. No matter what the setting is, Auto, or IGMPv3, the router seems to fall back to IGMPv2 when certain IGMPv2 speaking devices are turned on and connected to network.

Honestly, I don't know the RFC that well, maybe it is desired functionality, but somehow I'd expect the "IGMPv3" setting to stay in the v3 and never fall back to v2 in any case.

Additionally, I seem to have multiple IGMPv2 devices, but not all of them trigger the Orbi to fall back from v3 to v2. Especially it seems that certain Print Services on my HP Laser multipurpose device immediately cause the Orbi to fall back to v2. I managed to disable a few of them, but sooner or later the Orbi will still fall back to v2 and that I haven't been able to identify anymore, as it's so random.

Anyway, does someone know the IGMP RFCs that well, or the Orbi implementation to explain, why IGMPv3 setting on Orbi doesn't force the router to stay in IGMPv3? Is that really expected? Auto probably will fall back if needed, but is the plain IGMPv3 supposed to do that as well?

Thanks.