I also noticed the pressing the rocker switches for the couplers only sounds the horn or bell which should be in the other rocker position.
For this part, there are no rocker switches in the remote besides the power switch. the coupler/horn and coupler/bell are single buttons. Holding the button down will activate the horn or bell while "double-clicking", pressing the button twice in less than about half a second, will fire the coupler. Inside the remote are just 3 buttons. One for horn/coupler, one for announcements, and one for bell/coupler.
As for the speed problem two things come to mind. First is a failure of the speed sensor and this seems most likely to me. It could be a broken wire or bad solder joint, or a loose connection to the board here, or one of the parts may have gone bad. Depending what tools and test equipment you have access to, this may or may not be something you can test. I would start by checking continuity between the solder points on the board and sensor.
The other possibility I can think of is damage to the micro-processor which would require replacing the entire board. There are several ways the board could fail that would cause this problem, but none of them are worth tracking down for someone that doesn't already have the knowledge needed to do so, and even for someone that could do so, it is probably a better use of time to simply replace the board. I'm unsure of Lionel's policy on ordering boards for LionChief products but I know you have to contact them to do so. You may have to send it in, really don't know.
JGL
