At this point you are just guessing and you need more troubleshooting. One of the hardest problems for mechanic is to not be able to replicate the issue.
? ? This is what I would do the next time it does not start. Spray some starting fluid into the air intake and if it starts to crank up then it's definitely a fuel problem. Starting fluid can be purchased at any Walmart or auto supply store and is good to have on hand when traveling. I am also sure there's YouTube videos on it.
EDWARD NELSON