Clients lose connectivity to Router when Streaming Netflix HD

Devices Setup

Router 1 – TP-Link Archer C60 (Floor 1)

LAN IP: 192.168.1.1
DHCP Range: 192.168.1.2 - 192.168.1.99
Channel = 11

Router 2 – TP-Link WR-840N (Floor 2)

This Router is connected LAN to LAN to Router 1 and setup as an Access Point.

LAN IP: 192.168.1.2
DHCP = Disabled
Channel = 6

This LAN IP on Router 2 is set via TP Link’s Smart IP (DHCP) but I have reserved it for Router 2 within Router 1’s DHCP.

The Problem

When I stream Netflix HD at my Chromecast connected wirelessly to router 2, other clients lose internet connectivity and ping to router 2 fails for as long as the Chromecast keeps streaming. However, everything is smooth when connected to the same router 2 via LAN.

Chromecast is placed at the far end of the house but I get enough signal power to stream in HD. The problem also goes away when Chromecast is brought closer to the router where signal power is stronger.