I hope I can explain this better than I can write a title. I just typed out a long explanation and deleted it because it was hard to follow. I’ll make it shorter and add a diagram.
I’ve had a home wifi network for several years now which operates on cel towers using this mobile router, which does not have all the settings a wifi router has.
https://www.amazon.com/dp/B07G5KWZ3H
I’ve added a new non internet connected network using an old wifi router. My main computer connects to the mobile router using wifi and the wifi router using cat 5. The wifi router network is for 3d printers and other machines that don’t need internet connection.
The problem I’m having is when the Cat5 is connected to my computer the internet over the mobile router develops huge lag times. It may take 5 to 10 seconds for a web page to start loading and some programs, such as Fusion 360, will not connect to the internet at all.
How can the home network on Cat5 be interfering with my Mobile Router over wifi? What settings do I need to check? Whichever settings are interfering will likely need to be changed in the Cat5 connected router.
Manually configure the Ethernet interface on your desktop computer but leave the gateway address blank.