@SnoHobo 

It would help if we know some of the things you have tried.

Somethings I do to make my router stable.

I start by power off modem, router, and pc. I power on the modem, wait, then router, wait, then pc.

I do not use QoS. I found it causes more issues than solves for most networks.

I always use separate ssids for the 5ghx and 2.4 ghz. That way I control what devices are on which network as 5ghz is faster but has less distance. I put my iot devices on the 2..4.

Make sure the firmware is up to date.

I tend to keep the wifi channel narrow to prevent interference from other channels.

If there is not a lot of other wifi around, I use auto mode. 

I always power cycle or reboot after making a router change as some do not apply until you do. Been burned in the past when I did not after a power fail a few weeks later. 
 

when I have had issues like yours, I disconnect usb and ethernet connections, reboot and see what if any thing happens. If nothing changes, then I disable one of the wifi networks, reboot and test and so on. Also I connect only one pc to the router with wifi off to test, then add one wifi network, retest and add things checking the results.

Have seen usb drives cause strange issues as they pull more power at times then the router can handle. May need a power hub.
 

A factory reset helps sometimes. 
 

Let us know if you find something.