Remote Control shows lines.

[bond007james]

Got 2 exploras in lounge connected with dstv switch.
The RF out of both decoders got coax cables joined and connects to TV IN to a triax 4 way splitter with a 12v power supply.
From splitter 2 cables go to 2 tvs in the house with ellies tv links.
The problem is that whenever I press any button on the A7 dstv remote or the tv remote,then whole lot of lines appear across the screen.
This happens on both tvs.
Otherwise the picture is clear no problem when remotes are idle.

Any ideas how to solve this issue ?

Thanks