Mine misses from the get go. The HLA's are working, oil is flowing from their bleed holes, valve springs in #1 are good, no sticking valves. Cam lobes and rockers and bearings are perfect. However, the spark plug is clean, whilst the others are sooty from the short running on cold start it's been doing lately. No valve gear noise of any kind, so that rules out the rocker gear.
Your oily plugs are likely bad or broken valve stem seals, quite common in crossflows. You also could have an exhaust valve seat recessing, taking up the lash adjustment in the lifter and holding the valve off the seat as it heats up and expands. Mine? Still working on it.