(2-part post):
Firstly, a little hint about posting long questions: Once you've run out of space in the question area, click 'Submit'. Then, when your question appears, click 'Post an Answer'. (Repeat if necessary). That way, your whole question remains in single thread.
Now to try to answer your actual question;
When you connect some devices (such as TVs, VCRs, DVD recorders, digiboxes, etc), the 'receiving' device can sometimes 'auto-detect' where the incoming signal is coming from. Other combinations don't always work so well, so you need to tell the receiving device which signal it should be working with.
It seems that your DVD recorder 'knew' that it had an incoming signal from the digibox you used to have, and automatically switched to recording from that source. However, your replacement digibox doesn't provide the signal which forces the DVD recorder to automatically recognise the signal from the box. So it records from its own analogue tuner, instead of recording the incoming signal from the digibox.