Not being able to select the address "00" or "03" on a Digitrax UT6d throttle.

[Bendtracker1]

In the Digitrax system, it is possible (and, unfortunately, not uncommon) to have more than one throttle controlling an address.  I happens whenever somebody does not dispatch or release an address and another throttle "steals" that address.  So, that really doesn't explain your issue when you could not select the address at all.

This was obviously not the issue, but it was the first thing I checked and was sure it wouldn't be the issue.

Frankly, the keypad behavior you describe sounds like problems with the "0" and "3" key contacts, where you first don't get any and then get it twice.  But, when that happens to me (with older throttles) I can usually get the number if I am persistent.

No, the keypad worked just fine. It wasn't sticky, dirty or not making contact.  The reason it didn't get the first digit was because it was allowing it, period.
When I got two numbers ie: 33 was because it pressed the the "3" button twice after pressing the "0" button first.

In your case, it seems like it might have been the command station that was fighting you, but I have no idea why it would.  Getting the same address with the same throttle in multiple slots seems really odd.  That may be the thing to ask Digitrax to explain.

It wasn't just the same throttle.
I used the first UT6d, then I tried using the DT402d (which worked), but I also used a second UT6d which acted the same as the first one I tried.
My guess at this point was it had something to do with the DCS100 or the UR93 (since I was using it wirelessly which I did fail to mention the first time), or a combination of the two.

So far it's been working as it should?