TP-Link Archer C7 (hardware version v2) is the most unstable-working router I ever had. It randomly stopped working at least once in two days.
Sometimes I had to restart it three times a day but Internet was constantly dropping (even when connected via Ethernet) and Wi-Fi kept disconnecting all the time. Now and then 5 GHz network dropped until I power cycled the device.
In summer 2017 I tried to upgrade its firmware to the latest version but nothing helped and I continued to reset the router on freeze.