Unknown device showing up on home network - please advise

Thank you for your feedback. I've got the guest network turned on for our work/school computers. We keep our personal devices on the main network since I was told devices on the guest network are not able to access the admin GUI. We have not had any guests this year due to Covid, so it's more or less worked out with the MAC filtering. 

Sorry if I wasn't clear regarding the unknown device. The issue only shows up when I'm logged into the main (home) page of modem's GUI, there are icons on that page (wifi, ethernet, coax, etc.) that indicate how many devices are connected when you mouse hover on each icon. When I hover over the wifi icon it indicates I have 2 devices connected on the guest network and we only have the iPad connected. When I disconnect the iPad and hover over the wifi icon it indicates 0 devices connected on the guest network. If I add the iPad back to the network and check the main (home) page, the icon indicates 1 connected device at first and then later on when I check it shows 2 devices connected again.

When I check the Connected Devices page of the modem's GUI, or the Telus My-Wifi app it does not indicate an extra device is connected, so there is no IP address and MAC address indicated. I've factory reset the modem and updated the passwords multiple times, and the issue seems to keep popping up. I've not had this occur before with another device so I'm worried someone is trying to hack our home network through the iPad and maybe the modem is partially catching the issue by indicating the extra device via the main (home) page of the GUI but nothing is showing up in elsewhere.