I found that once the channels had scanned in, they worked, even via the V-Box II, that is after I had changed my cable, which had become damaged.
When I first moved to this house, mainly for the open, south facing, garden, so that I could fit a ground stand, for my dish, I fitted green, waterproof, cable, which was quite expensive, so i thought it would last longer.
Unfortunately the sun made the cable brittle, after a number of years, so that when I came to adjust it, it cracked, so i replaced both cable runs with new WF 100, and also used this for a lead, from my V-Box II, to my receiver, and it's worked better ever since, although it still has problems scanning in some frequencies.
Try connecting both tuners to the cable directly from the LNB, one at a time, then manually scanning in the channels, without the other cable connected, both should work, but if you connect both of them to the V-Box II cable, I doubt either will scan in the channels.
You can try fitting better quality cable, even WF 125, but this is a lot thicker, and it's not easy to bend, or run it around corners.
Once you have your channels, and bouquets, organized use Dremboxedit, to save your channel list, then you shouldn't need to use Vhannibal's, or Catseye's lists, but re-load your own, after any new image.