
Having looked back through this thread..
You seemed to have this problem with the decoder to start with..
You did however have a second loco on the track. - did you change any CV's during this time?
If you did, it may be that BOTH loco's are now on address 3, so both may respond to commands sent to address 3.
Please make sure there is only one loco on your track whilst doing further tests. - Probably are doing this, but we can't see down t'interweb to your setup.
It may be the correct sounds are loaded, but the decoder has not been told which sounds to 'play' for which button pressed??
We probably need to wait for Neil to chip-in, as it appears he has used QSI decoders..
You seemed to have this problem with the decoder to start with..
You did however have a second loco on the track. - did you change any CV's during this time?
If you did, it may be that BOTH loco's are now on address 3, so both may respond to commands sent to address 3.
Please make sure there is only one loco on your track whilst doing further tests. - Probably are doing this, but we can't see down t'interweb to your setup.

It may be the correct sounds are loaded, but the decoder has not been told which sounds to 'play' for which button pressed??
We probably need to wait for Neil to chip-in, as it appears he has used QSI decoders..