Why did the Asus router start cutting the incoming speed?

Question

network hardware

DD. Asus Rt-AC68u stood for several years and did not know any problems, but a week ago it started showing download speed < 1mb/s, while upload 90-95Mb/s as usual. No settings have been changed on the router. The provider says that he also did not touch anything. I sin on the router because I installed another one (dlink d-300) and it shows full speed. At the same time, if I connect the Asus Rt-AC68u patient to the old router, then he also starts to give speed standards. Those. The problem is when Asus is connected via WLAN.
What did / tried:
1. Updated to the latest firmware. At the same time, he himself did not see the firmware (he could not connect), downloaded it manually and uploaded it, like there were no glitches. + provider reset some errors from itself. The speed rose to 5-10mb.
2. Reset to factory settings. I set up only the network, which is without authorization and everything is on the machine, and the login / password from the admin panel
3. I ran through the settings, switched different modes, turned off / on different monitoring services, etc.
4. Rummaged through the router log and didn’t seem to find anything
5. Lan speed tests, wifi 2.4 and wifi 5
6. Speed ​​tests inside the admin panel show the same

update.
7. Transferred WLAN to other LAN ports and the history did not change

tests from the admin panel when connected via d-300


when directly to WLAN

Answer 1

The problem may be in the cable from the provider. Some degradation in performance (e.g. due to insulation damage).
The difference between Asus Rt-AC68u and D-link DIR-300 is that Asus has gigabit ports. In practice, they are a little more capricious about the quality of the cable. Those. jambs appeared, but DIR-300 forgives them. And on Asus, packet loss occurs, which leads to your result. If it were possible to look at statistics on packet losses, then they would confirm or deny this version, but Asus is unlikely to have such a function.

Answer 2

Have you tried resetting to factory settings and reconfiguring?
Still, as an option, the WAN port could burn.