I also have had this happen on glow engines a few times over the years. Always after the engine had just quit. In fact I've even done it intentionally(after seeing it work on accident) when a engine died right after I removed the glow driver. on a good running engine(not rich idle) you can even "kill" it by dragging your electric starter on it and relight about a second later fairly often(safety geeks use your safety cage and steel mesh gloves please). As Far as the full scale issue, there is a video on the web that shows starting a Sopwith Camel by turning backwards to prime, positioning at TDC, the flipping the mag on. So it could be as little a "wiggling" a intermitent ground. One thing I've learned in being a mechanic for 20 years is (myself included) Don't assume that your gonna "see it all" in a lifetime, much less in 20-40 yrs. I've had to eat my words before on units I've rebuilt 1000's of! Ever heard of greasy shop rags spontaneously combusting in low humidity? Ynow those funny red triangle "hampers" you have to put them in?? Todd