Sharing TV with Cable Box?

I'll admit right off the bat that I'm a noob when it comes to this stuff. I recently purchased a Beelink thin client to use as a media machine. It runs Windows and I have VLC, etc on it. I have a 6TB drive full of media and a fair amount of it is in a format that my Samsung TV won't play, so I decided to get this Beelink set up with the 6TB drive and use HDMI 2 on the TV to display this media as an alternative to cable. My Spectrum cable box is on HDMI 1. Sources sit in a media cabinet and are connected via HDMI cable run through the attic to the TV across the room. This setup (minus the Beelink) has been working for over 3 years. I had a Firestick in HDMI 2 originally and it worked fine.

When I removed the Firestick and plugged the Beelink into HDMI 2, the cable signal goes dark on a regular interval every few seconds. This happens even if the Beelink isn't powered up. Both the Beelink and the TV are connected to the Internet via my cable modem. Is this some anti-pirating feature built in to the cable box? If so, this makes my whole plan null and void......uggh. Is there something I can do to avoid this? I'm trying to avoid Spectrum "help" line hell so any suggestions would be appreciated. Thanks