Black screen (no picture) on Component output, but fine under Composite??

I recently picked up a standard NTSC Xbox at a garage sale and upon bringing it home to mod, noticed no picture output when hooked up to my official Microsoft component video breakout box. Fearing that my breakout box had given up the ghost, I tried hooking the cables into a different component port of my TV. Still no picture.

I also tried the same thing with another set of third-party cables with zero luck. In a last desperate bid, I pulled out the composite/S-video cables the system came bundled with and hooked those up...Boom! Picture came up fine and everything was free of distortion, under both s-video and composite.

The model is a 1.6, manufactured in late 2005. I took apart the machine and inspected the board. All caps, power supply and board overall looked just fine. I cleaned the video port pins, reassembled the Xbox and retested everything with the exact same results.

While I'm thankful that my component breakout box is okay, I'm a little confused as to why there's an issue with the video output. Has anyone else experienced similar issues?

Thanks!