TV keeps jerking, what to do?

We bought a new LG 50UM74 and every few seconds the picture freezes / the sound cuts out. But that's only the case on TV, Netflix works perfectly. We have a satellite connection, with signal strength around 80%, with signal quality 100%. In addition, Austrian channels can't be received. I'm grateful for any help.

Are all channels jerking or only certain ones? Have you already checked the connections of the antenna cable, and your own dish or via a house distributor and multi-switch?