I have Bachmann 44-tonner, doodlebug and EZ-Command DCC. all work fine. Just added a Bachmann FT-A w/ DCC pre-installed and while it runs fine and quietly at moderate speed, at low speed it screeches and chatters. Is this the nature of this particular model series, or is it a problem to this particular model and thus due for repair or replacement? It's a week old, purchased new via mail order.