I am having trouble with the DCC Bachmann AE32071 DCC Sound Decoder I purchased a few weeks ago. Specifically, the locomotive (a DCC-ready Bachmann 2-8-0 n-scale) hums when power is applied, sputters under throttle (starts – stops – starts – stops...) when going forward and in reverse, and when my DCC controller is in reverse, the locomotive moves slowly without the throttle being applied. I must either apply forward throttle or disconnect the power to stop the locomotive. I installed the speaker but did not connect it to the decoder. I have not soldered anything on the locomotive or decoder.

I ran through the following troubleshooting steps:
- I tested the locomotive with and without the new DCC decoder on DC power. The locomotive runs smoothly with no hum. Other DCC locomotives that I have run smoothly without any stuttering or humming. Based on these, I concluded I have good track electrical connections, sufficiently cleaned my track, and have not damaged the pickups or wiring on the locomotive.
- I thought it might be a I have pulse-width modulation or BEFM issue, so I reset and tested the locomotive on DCC with a sampling of CV 211 (PWM) and CV 212 (BEMF) settings (min and max values, plus every 8-10 steps in between). I tested each separately and performed a factory reset (CV on the decoder after each. I did not make any adjustments to CV 209 or 210.
- I got a new decoder, thinking the first one was defective. The symptoms were identical.

Any thoughts on how I resolve this before I return the locomotive and decoder?