I have had trouble with some boxes so too determine if hardware or software issues I try the following. Use Toysofts OpenBlackHole 1.4 and see if you problem still exists. If tuner issues are gone its a software issue with your setup. If it still persists its hardware. OpenBlackhole 1.4 is a good base to check with as always works well with all boxes.
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DM800
DM800SE
DM800SEV2
VU+ UNO
VU+ DUO
VU+ DUO2
VU+ SOLO2