I do not understand why there are IP addresses that do not belong to my network. I hope someone can help me understand why this is happening.
Those are users who joined your network but could not complete the DHCP request, likely you will see error messages about DHCP in the log.
The users will continue to use the address they got from the previous network they connected to, or the fallback address 169.254.x.x.
Of course they will not be able to connect to your network until they complete a successful DHCP.
Sometimes the cause can be that your DHCP server has a too short leasetime, increase it to at least a couple of hours, better 1 day at least.
Thank you!