Network difficulties

A bit long, but I hope someone will be able to help me. 
My home network consist of 2 devices:
1. Internet router with wireless capabilities. 
2.  TP-link archer vr600 that act as a WiFi extender that extend the network coverage. (through wds bridging). 
Both are working on 5ghz, both networks have the same IP range (10.0.0.x) and have the same ssid in order for the network to work seamless. 

My wireless devices:

-smart tv (lg smart tv) which is located in the living room, closer to the access point so obviously it connects to the access point. 

-PC connected directly with a cable to the internet router

My problem:
I am casting videos from my pc (casting from chrome and other apps) to the tv. 

Whenever the tv is connected to the access point, the cast is not working (the option is actually disappear). 
When I connect the tv to the router (in order to do that, I power off the access point, and connect the tv to the router) the cast option is working perfectly! 

Obviously I prefer that my tv will connect to the access point because the signal is perfect. 

Any thoughts on what might be the problem and how to fix that?

Thanks you.