Why multicasting is so poor on WiFi?

[gjf]

Asus RT-AC68U with Merlin 386.1_2.

The provider broadcasts IPTV via multicast.
The router has the following simple settings for IPTV:


I have two mediaplayers in this network: one connected by cable and one - by WiFi. Both are the same in the meaning of model, firmware and settings.
Both shows a good connection (in meaning by speed) and good video playing (for online cinemas)
Cable connection works like a charm for IPTV.
WiFi connection shows freezes after 20-30 seconds of playing IPTV.

Taking into account all circumstances I think the problem is in router.

I've tried to disable multicast routing at all and to enable UDP Proxy. But in this case IPTV is a nightmare at all - I think router has no resources to work in proxy mode.

Any other advices?

I'm attaching Wireless settings just in case:

 

[Wade Coxon]

I take it the problematic media player is on 2.4GHz then?

Turn off Explicit Beamforming, and set the multicast rate to Auto.
Any reason you are limiting the modulation scheme to 802.11n?
And drop your channel width to 20MHz. 40MHz in the 2.4GHz is asking for trouble.

 

[gjf]

802.11n shows better performance on other WiFi clients. So that's why it was set.
Although I've tried your advices as well as setting modulation scheme to auto.
It doesn't help either.
And yes: problematic media player works on 2.4 GHz only - that's why I didn't post 5 GHz settings.