Sounds like possibly a combination of inadequate power and/or possible voltage drop across a particular section of your layout. Are the problems seen with only one loco on the layout, or when you have more than one loco on the layout? If it's the latter, you may simply not have enough power (wattage) for multiple locos, particularly if there is one or more voltage drop(s) on a larger layout or a bad section/connection or two.
As for the Lionchief couplers, read the manual carefully as to operating the couplers (if they are operable by the remote). For some earlier models it requires rather fine control of the coupler buttons, which serve dual purposes. In more recent remotes, you hold down the shift button and the electrocoupler button which is much easier. Check and see if your remote has the shift button (lower middle button) or just a sounds button (speaker image on the button). The latter, earlier version remotes require more challenging button pushing skills to get the electrocouplers to work without sounding the whistle or horn.
