Power Loss with RealAir Duke?

After flying the RA Duke for about one month, I'm experiencing unexplained power loss. Firstly, FL240 MP 32", 2500 RPM, FF 114 PPH, IAS 150; everything normal. Thence, gradual power loss over the span of about 45 seconds to less than 14" ! Attempts to correct with mixture changes are futile. After about another 45 seconds, power returns on a gradual increase at about the same rate as the decrease. Assuming this is weather engine related, I'm using ASA with XG/FEX graphics. Now, following and emergency descent to 16 000, think once again normal. This is the second occurrence over two days. Les Parson