I tried installing an EZ Command decoder in my Athearn AMD-103 which has a an 8 prong plug and it just doesn't work. For one the decoder doesn't seem to stay put with simple fingure pressure and comes out easily. Also does the bachmann decoder come pre programmed for channel 3 or does it require the use of the programming track?
Are you sure you have the decoders plug turned around the right way? The decoder is preset to address 3. Bachmann decoders are designed to be programmed on the main but can be programmed on a programming track as well. BTW, I hardwire all my decoders. I've had the same problem with Athearn's that you're having.