Additional Hidden SSID coming from my tp-link (Archer 1800) Router.
When viewing my network with a WiFi analyzer app, I'm seeing an additional network with a hidden SSID. This network follows my usual network whenever I change the channel, and goes away when the router is disabled. To my knowledge this was happening on both my 5 GHz and 2.4 GHz networks, but following a full router reset it is only being seen on the 2.4 GHz channel (I'm doubting my memory now though...). The mystery network seems to be intermittently active (WiFi scanner app updates every 3-5 seconds, this network appears on approximately half the scans) and has a MAC address that is identical to the main network but off by a single digit in the last field. Following the reset, all devices were kicked off the network and my laptop was added back on.
At this point I'm very sure it's coming directly from the router, but can't seem to find details regarding this. Searching online I couldn't found any solution of this issues. This seems to have been discontinued (every link I've seen to details online are dead now or redirect to a general info page. It may have been called "WiFi Connect" or something like that), but I'm wondering if some models of routers still generate a separate network for this purpose.
I definitely want to turn this network off, so if someone could point me in the right direction that would be great. Also any info on the Thread/ program would be appreciated. Router model is tp-link - Archer 1800. Thanks!
Edit: To provide more information, I don't have any third party shield or anything like that (or Bluetooth headphones, & I wouldn't suspect that), but regardless all devices except for my MacBook are now off the network following the reset. I have gone through all the router settings and haven't found anything that seems directly related but I could have missed it. I am on an internet only plan, so no set top boxes or any additional hardware (no signal booster either). However, installed next to my router are two boxes one of which appears to be the optical fiber receiver, and the other looks to be powering it. The receiver is connected to the router with an Ethernet cable.