What is the problem with TV signal interference?

Question

Iron

In general such a problem. I've already broken my head.
There is an LG plasma. it has an Online Telecard.
There is a PC standing under the TV about a meter away.
And suddenly such a trouble began: the image on the TV set began to lag wildly. at what point - I don’t remember ...
BUT! When the PC is off - everything is ok. The picture is perfect.
I thought it was a cheap HDMI - cut it off, it did not help.
I changed the router at some point, around the time the lags began (Kinect 2). I tried to pull the cable from it from the TV - it did not help. I cut down the router - it does not help.
Another PS4 is under it with HDMI, but the interference is when the computer is cut down.
I changed the video card and power supply, but after the start of the lags.
Lag ONLY on TV broadcast. Coax signal, but digital - DVB-S2
The computer is powerful, connected to the UPS. TV in another UPS, but not in the battery connector, but just passing through. But somehow it doesn’t fit, because. The UPS is always on, there are speakers and a router and a curling iron. Yes, and the TV set does not lag if the image from the curling iron or PC comes.
What could be the problem? Help, my wife is already arguing ((

Answer 1

Do grounding?

Answer 2

Consider the options for the problem:
1. Computer power supply
2. UPS
Consider the solution:
1. Move the computer away from the TV.