This is still happening. I'll be returning this device on saturday if I don't get any support. Your email people never got back to me either.

Every device on 2.4ghz: [16384.123168] wlp2s0: send auth to 50:c7:bf:f9:ea:d7 (try 1/3) [16384.125009] wlp2s0: authenticated [16384.127792] wlp2s0: associate with 50:c7:bf:f9:ea:d7 (try 1/3)...

c2300 is garbage. It doesn't handle 2.4ghz, and basically a single ban 5ghz device.

I have much the same issue, seems like replacing the router with one from a more reputable manufacturer is the only solution.

I have the wifi password correct, yet multiple devices connecting to the 2.4ghz connection get deauth'd with a "Class 3 frame received from nonassociated STA." There is little noise, this happens...

Sounds like user tracking behaviour that breaks the GDPR to me.