First of all, disconnect and move the "working" dm into the bedroom, see if it works correctly when connected to the spare cable.
If it does work the same, then there is a problem with krazy cam or the second dm tuner.
The transponder lists may not be the same. Compare the transponder lists from both dm's.
You can also try the "bad DM" with the "good" cable.
You should be able to figure out whether the dm is bad or the second cable.