Yes. Coax is very fickle. It’s really easy to cause interference or mess up the signal one way or another. Even the change in temperature over the seasons has a strong effect on signal strength.

Call the ISP to get it fixed. Or if you’re up for the challenge, buy a coax stripper, a coax crimper, and some outdoor rated type-F connectors and fix it yourself.

They also left you like 6 miles worth of slack for no reason.

Welcome to the world of Coax and why I’m so damn glad I got fiber now.

VLANs work on layer-2. A switch can isolate frames between VLANs and that’s it.

You need subnets and a firewall if you want them to communicate with each other (layer-3).