My dad bought a used Jeep Rubicon that was all stock except an aftermarket alarm. Sometimes it just wouldn't start, but if you tried again later in the day, it would fire right up. I suspected it was the alarm, and we both feel that alarms are worthless (when was the last time you saw someone give half a crap about a car alarm going off?), so I pulled it out.
Lo and behold, scotch locks and crimp connectors everywhere. I guess they worked OK for a few years, but eventually the wires inside the scotch locks broke, and things stopped working. I cut the damaged section out of each wire and properly soldered them together, using marine heat shrink. Has never missed a beat since, and looks almost factory.
Because of how often I see abominations like this done by so-called professionals, I end up doing all my own wiring. Actually, I should make a thread for the stereo mods I am doing to my Duraburb. Not the LUX amp swap (thought about it, have one sitting in the garage even), because I wanted to try something different with the sub setup. Hopefully I get a chance to wrap that up in a couple weeks, and I'll post up a thread & photos.