If it is that intermittent AND electrical, then it is likely a crack in a sparkplug or loose crimp in a wire or crack in a coil or other wire that causes it, and it could be a devil to solve quickly, short of "winging" it and replacing a component or set of components at a time.
Think about what electrical bits that you've replaced with new over the past year first. But, we don't have evidence yet to point us to electrical source versus fuel source without more data. I am not saying to start tearing out electrical parts yet, but consider the following 'checklist' of electrical items:
1. New spark plugs? Replaced when? Check for visible cracks though internal defects (unlikely, but probability is non-zero) would be invisible.
2. How old are your plug wires? Check both ends for good solid connections
3. Do you have a new coil, or at least a non-OEM "gray" crack-o-matic coil?
4. Have you taken the ICU off its aluminum bracket/heatsink, cleaned up the surfaces with fine emery cloth, and reapplied heatsink compound between the metal back of the ICU and the aluminum heatsink? (This should be done periodically, ~ 5 years or so depending on climate)
5. While there could be a sticking advance mechanism in the ignition trigger unit (bean can), I don't think that it would just stick that one time and never again. But, if we get down to eliminating everything else.. don't go here until there is strong evidence pointing to it, or have completely eliminated everything else first.
Think back about the conditions when the problem happened - was it very hot&humid, rainy, dry, etc. Had you recently filled up the gas tank from a "different" petrol station? Had you done anything to tick off any Jamaican witch doctors?
