If you are losing channels slowly one by one then it's a big possibility that the tuner is fading or it needs a firmware upgrade. A new channel list on a box with problems will not fix those problems. Do a factory reset--upgrade firmware--install channel list then see how it runs.
Also no signal can mean many things i.e cables, lnb,dish,dodgy ox and so on---invalid signal means new list required etc etc.
Reaper.