Repeated Wi-Fi connection attempts are not fully blocked

[StR]

I've been getting these lines filling up system log of RT-AC86U, about 18 times per minute.:
eventd: wlceventd_proc_event(530): wl0.2: Auth FC:67:1F:40:92:C7, status: Successful (0), rssi:0
This is not one of the devices that was given credentials to my network.
When I look at the "Wi-Fi" log, it shows that it is connecting to one of my "guest" networks (2.4GHz) (with the name "guest" in the SSID)
When I turned of that network, it started connecting to a different guest network (without "guest" in the SSID).
When I switched the channel number, the connection attempts stopped for a while, but then restarted.

It doesn't seem to be authenticated, so, I am confused why that log line says "Auth ..., status: Successful"):

Also, I added it to the Mac-Filter "reject" list:

So, I have two questions:
1. Why does the system log says "Auth status: Successful"?
2. Why does this happen despite the Mac-filter?

(I suspect it might be one of the IoT devices that is trying to do that, maybe even one of ours [I am reluctant to connect the stove, fridge and whatever to the router, as I don't need their connected functionality], - or maybe one of neighbors'.)

 

[EPR]

I saw your reply to mine. I have not seen my gremlin in about 4 hours now, so maybe...

Did you reject the MAC in, guest network > select guest network where located > very bottom, enable mac filter > reject...

I tried wireless > mac filter > first, no go

 

[StR]

I saw your reply to mine. I have not seen my gremlin in about 4 hours now, so maybe...

Did you reject the MAC in, guest network > select guest network where located > very bottom, enable mac filter > reject...

I tried wireless > mac filter > first, no go

Thanks a lot!
Indeed, if it is set in each of the guest networks, it works.

I still don't understand why it was saying "Successful" in the logs though...