I don't have a DCS51 or a DCS50. That said, I think a factory reset might fix your problem. Here are the instructions from the Digitrax web site:
To reset the DCS51/DCS50 to factory settings:
If you change command station option switches and experience unexpected results, just set OpSw 39 to “c” (closed) to reset the unit to the original factory settings.
1. Press the PROG key. The display shows the last decoder programming mode used.
2. Press the SWITCH key. The display shows the last switch used and its commanded position.
3. Use the numeric keypad to enter the number of the Option Switch you want to change; in this case 39.
4. Press the "c - / CV-WR (lower right of keypad)" key to set the OpSw to closed and reset DCS51/DCS50.
5. Press EXIT when finished. The DCS51/DCS50 display will show "-cS-" to indicate that you are running in command station mode.Hope that solves your problem!Bill