Lionel Uncoupler Track

[srguy]

I'm having some performance issues with engines passing over the Lionel O uncoupler track. The engines seem to slow a bit while passing over the track. Additionally, I have a Williams FM that looses the horn and bell sound while passing over the track at a slow speed .... the horn and bell generally works when passing over the track at higher speeds however this engine is powerful and running at more than 12 V it's going too fast. The track was pretty dirty so I cleaned it last evening but no improvement. Any ide what might be going on here??