Adam,

I have seen this problem twice. I agree that it is very strange that the code would work on its own when you test the number 6 but not in a macro. First, I draw from what you said earlier that other channel macros without the digit 6 operate normally. If that is the case the durations are correct etc. Replace the number 6 code with that of another codeset for your Sky box.
Here the number 1 has caused that same problem with Scientific Atlanta receivers. There is something peculiar about that code that allows it to work individually but not in a macro. If the code doesn't work in a macro, its bad code. Good luck.

Stan Kay