Generally speaking, the electronic units like these that I have seen failed were due to the heat (and on some bikes, vibes) that comes from being so close to the engine.
The electronic components used for triggering purposes must be severely restricted (in power applied) at the 250 degree temperatures found in that area to prevent internal meltdown (literally!). In addition, solder, which is not terribly mechanically strong, will "migrate" away from the metal component legs and contacts when heated a little, then cooled, over and over. Eventually, the solder becomes granular and the contact area diminishes until an open circuit occurs on the PC boards somewhere. This was the biggest item I used to see on the old-style Dyna S units (they are somewhat better, now), and all of the Boyers that I have seen failed, and the several Martek units I have post-mortemed. (BTW: one of my professional skills is Electronic Failure Forensics.)
This problem is one of the stumbling blocks I'm having with the LED timing light add-on for my Ignition: although it only runs when you're actually checking the timing, the tiny PC board has still shown these same symptoms within a few months of being installed onto the points plate. So, I'm having to either spot-weld the components together (which can damage them internally), or remote them somehow from the engine (which I really don't want to do...). It's a gnarly issue!
