It must be a problem with the plastic airframe.
I owned a Sonex for 10 years. It ran an early Jab 2200 which I think was serial number 65. I flew this thing all over Australia including three Bass Strait crossings. It ran hot, it had no compression, it blew oil out the breather as fast as you could pour it in, the spark plugs were black and sooty and needed changing every 50 hours, and most of the time it was at full throttle, because in my book max continuous power is there to be used. Gentle cruise power is a woftam. It never missed a beat despite once running the oil so low it took almost the full sump capacity to top it up.
Maybe it was the crystals in the metal airframe? If Peter Brock was still with us, he would know.