The design of the engine with a cantilever crankpin is more prone to flex than a double crankweb design. The advent of synthetics made it possible to extract a serious amount of power from this design, which is taken to the limit in the 26cc engine. These engines will not, I repeat will not, tolerate anything less than the best quality two stroke all synthetic racing oil.
Bearing failure will occur if the lubricity of the oil is reduced by either running the engine too hot, or using inferior oil.
Pistons are not that sensitive as long as a fair amount of slippery stuff is present. The MVVS graphite coating makes it even more durable.