Originally Posted by Subcrit
Thanks. All my other 12V devices work just fine. I do not think this is the issue.
I am thinking this an issue with the strip itself.
Some strips have "sets" of LEDs to manage the voltage drop along the strip and have "cut" spots marked along the strip and some are made with single LEDs that are actually 3 or 4 in one square unit. In either case there is a resistor to manage the current flow to each part of the set of LEDs.
Brightness is a function of current; which is set by a fixed resistance in "on/off" strips and a variable resistor in dimmable ones.
In these strips, the resistors are "flat mount" types and are surface soldered to the plastic strip. A break (where one end of the surface mounted resistor becomes disconnected due to a crack in the solder) can shut off one of the LEDs in the set dimming the output of the track.
Replacement should fix your problem.
If you feel frisky, here is a how to manual on LED strips.