Hi!

I have an Archer A6 router with one desktop PC(wired), TV(wired) and four laptops(wireless) connected to it. Two of my laptops are pretty old and have wi-fi modules with only 2.4Ghz band support. They work fine. Wired connections are also stable. My problem occurs only with those devices which have both 2.4 and 5 Ghz band support. My internet connection speed is 600Mbps. Everything works fine for first 15-30 minutes after the router restart/reset, but then internet connection suddenly slows down to a point when I cannot even open any webpage, speedtest shows either near-zero speed or connection error, but wired and 2.4Ghz only devices keep working fine. On the rest devices with 5Ghz band support both 2.4 and 5 Ghz bands are affected, switching between bands doesn't help.

I have upgraded the firmware to the latest official version available for my device, tried to do hard reset, change channels, disable 'SPI Firewall', 'MU-MIMO', and finally I've figured out that disabling the 'Nat Boost' option solves the issue completely and immediately without even need to restart the router. The problem is that with 'Nat Boost' disabled I get only 150-200 Mbps on my desktop machine vs 600-650 Mbps with 'Nat Boost' enabled, which is very frustraiting.

What could be the reason for such problem, and is there any way to fix it?