I have a similar issue with an MX-900 controlling a (UK) Sky satellite box. Using the codes from the DB, or learnt from the original remote makes no difference.

The up/down/left/right buttons (and some others) will act as if the button has been pressed multiple times if I leave it on 3 repeats. It even does it sometimes if I have it on 2 repeats, so I've ended up setting it to 1! That seems to work OK, but as with Daniel's problem, I've had to turn off the 'repeat while pressed' or, again, I get multiple activations. It's rather annoying :( I didn't have this problem with a Harmony remote, although that was otherwise a much inferior product.

Daniel - I'm using a workaround for the 'hold down the button' scenario, which may be of interest. Forgive me if you've thought of this already :)
I've set up press and hold macros for the buttons in question. The initial press sends the code with repeats set to 1, and 'repeat while pressed' turned off. The hold macro does the same thing, but with 'repeat while pressed' turned on. Now if I hold down the button it will start sending the code continuously and act like the original remote. Unfortunately, the minimum hold delay time is 1 second so the response is rather sluggish compared to the original remote. (Surely it wouldn't be hard for the software to allow for shorter delays?) There's also no indication to start with that anything is happening, which feels a little awkward. Still, it's better than being stuck with single presses only...