R7000P - Incorrect Password on 2.4GHz and 5GHz down to 1/10th normal speed

As everyone probably suspects, the factory reset of the router did not help with resolving the aforementioned 2.4 GHz and 5GHz issues.

I think I figured what fixes them.

After updating to the latest firmware (V1.3.1.64_10.1.36), the issues persisted.
I contacted Amazon so I can arrange for a return and started searching for a replacement product before sending this one back.
I tried changing something just to test.
I set the 2.4GHz channel from AUTO to 11 (was the best possible according to some WiFi scanners).

I also changed the power adapter from the UPS to the mains directly.
I recorded an uptime ot 19 days without any of the two issues before a power surge rebooted the device.

I then plugged the adapter back to the UPS and the uptime is 8 days so far. No issues whatsoever.

2.4GHz devices are connected and running.

5GHz band does not drop Internet download speed to 6-7 Mbit and sits at the maximum possible.

Unless this is some very weird coincidence and the problems are just not happening for an unusually long periods of time, then the issues are resolved.

So to sum it up. If your 2.4GHz network drops devices (incorrect password) or your 5GHz network lowers download speed randomly, set the channel of your 2.4GHz manually. This seems to have been the solution for me so far. Hopefully it stays that way.

I have always had issues on my previous routers when not setting the channed manually, but figured that this much more expensive router will be able to figure it out on its own. It seems that I was wrong.

Hope this helps someone and saves them the hassle of dealing with this.