Could you please post some pictures?
Seeing exactly what the offending section looks like would help.
Also 20+ what? Feet? Yards? meters? Wombats? (granted the last 3 are about the same length... :-D)
It sounds to me though as if it is simply propblem of track connections not being perfect:
See the section about power drops here.
Tightening the tabs is vital for a good connection.
Also if the raiels are tarnished in any way that will degrade power.
The usualy track troubleshooting applies: Does the problem occur when you connect the section of the track directly to the powerbase?