We have a Zinwell 620HD and a MagicTV 3600

We can see Mt KauKau in Wellington

Recently two things happened - first there was the retune about a month or so ago & around that time our good quality belkin RF cable was damaged.

I got a replacement white RF cable from bunnings.

However, the Zinwell 620HD which has this cable can pick up TVNZ + the kordia muxes fine but it keeps showing the signal/quality meters for Mediaworks dropping every second in the manual channel mode. For the brief second it sees it both strength and quality bars are quite high.

The MagicTV shows the mediaworks solid (at 100% quality, 71% strength)

I have tried the manual settings on all combos of the following
570000 / 569950 / 570050
6mhz / 7mhz / 8mhz
priority low & high

But it still does the same pattern of showing strength+quality for a second then gone.

Any ideas?