It's a rather odd situation I have come across. My DIR-825 (H/W vG1) works fine for a few hours on both Wired and Wireless (2.4GHz and 5GHz) connections. After a few hours, the Internet just stops working on the WLAN. I can access the local network just fine. I've checked the WiFi channels in the vicinity of the router and there is a maximum of four 2.4GHz devices mostly on other channels and very low strength. I set the router to use selected channels and even then after a few hours, it won't work. I've tested this problem on a couple of devices and it's the same. Both 2.4GHz and 5GHz stop working. The odd thing is I can ping to Cloudflare DNS or get my IP address through IP Tools (Android App) just fine, but if I try to browse something or do a speed test, I get "Check your Internet Connection" error. If it helps, there are a maximum of 35 devices in the network, and on average 20 devices are connected to the router, but most of them are connected through other Access Points in the network. The DIR-825 has a maximum of 10 devices connected directly to it via its WLAN. The only solution yet is to restart the router every time it happens but that's not always feasible.
Any thoughts?