Casting (Youtube/Netflix/etc) not working on different VLAN

[warheat1990]

I have VLAN for IoT. Chromecast and Google Home Speaker is one of them. I'm not able to cast audio/video to Chromecast/Google Home so I installed mDNS (os-mdns-repeater) plugin and turn it on for both IoT and my home network. 
 
The Google Home speaker works (I can now cast my audio from my phone/PC/etc), however I can't get Netflix/Youtube casting to work (it won't detect my Chromecast/TV with casting capabilities). 
 
Weird thing is I turn off mDNS and audio casting still works. 
 
Any idea why?