It's not a flat camshaft. You'd notice that at idle. It's ignition.

With an inductive pickup timing light, the one where it clamps over the wire, check every wire up to the rpm range where it starts missing.
In other words, put the clamp on the #1 wire, pull the trigger and watch the flashes as you go through the rpm range where you get the miss. Do this for every cylinder.
You will probably find that one or two cylinders have gaps in the flashes as you get into the range where you notice misses.

When you have narrowed it down to two or however many cylinders, change the plugs in them and retest. If it still keeps happening, swap wires with known good and retest.

I believe that what you are seeing is the result of carbon tracking or a bad plug, and when the cylinder pressure reaches a certain amount, the resistance across the plug gap is more than the resistance through the carbon track or plug. Voila! Misfire happens.

Last year I changed the plugs and wires on my wife's 4-cylinder, using Autolite plugs and Beck-Arnley wires. After a few months the car would occasionally have a stumble at idle, just enough that you'd notice it. I couldn't figure it out.
I was out of town, so she took it to the local garage and the guy correctly diagnosed it as ignition problems. There was carbon tracking in the plug boots. I would have never expected that as I had used new brand-name parts specifically built for the engine in question. But, changing the wires and plugs solved the problem completely!

R.