@Jashua_Bat2022 Yeah disable any DHCP in any router/AP that is not the ER605.  The screenshots are very helpful, there should be no clients with an IP address starting with 192.168.0.X or 192.168.1.X, these are coming from other DHCP servers.

I can't tell which switch port is connected to the ER605, but make sure its profile is "All" or "AllVlans" if it has all three VLANs

Then based on what you have posted.  Ports 12 and 15 need to have the profile changed to "None_Work_at_Home"

If Yellow Switch on port 12 needs more than one VLAN, you will also need a profile that includes both VLANs with the native network being "None_Work_at_Home".

  @Jashua_Bat2022 

Also check if you enable the "Leagl DHCP server" option on network->LAN settings.

  @Jashua_Bat2022 I hope you understand my English.
I think I've found the solution, I blocked the client with the wrong IP address in the clients section then I went to the insight section and pressed the forget button beside the client then I would unplug the cable from whichever port then re plug it, also I would reboot the client's router, afterwards when I go check its IP address it now has the correct IP address.

Edit: I still don't know what's causing this issue, the important is I have a way to fix this even though it's quite a troublesome.