I don't think this is a problem on the Rotax 912. I have 550 hours on my engine and have cross checked the pitch of the two blades many times and they have not moved. I have also checked the torque on the bolts with no problems there either although a couple of RV12s have shown some loosing of these bolts. Back in early 2011 I sent my blades and center hub back in to have them redone. There was some abnormal wear on the shaft that was clamped in the center hub. That's when sensenich started making a change to their hubs. It all started on the RV12 in December 2010. See this thread here:
http://www.vansairforce.com/community/showthread.php?t=66335&page=2

On this form there has been two problems reported on other engines manufactures with the sensenich prop. The first one was the ulengine and now from your report the Viking engine. So for now monitor you bolt torque and blade pitch and keep on flying:D
 
As stated, Rotax people should not read too much into the reference (which is my build log by the way).
We don't use the same prop, first of all mine turns backwards from the Rotax. My prop model is 2AOR5-D, however the sticker on it says "2 blade Rotax hub". I have found that the clamped portion of the blades are not too precise, and differ in diameters of the clamping area, as well as different weights of each blade. These problems MAY only be found in the reverse turning blades. The UL problem appears to be unique to the UL engine, and is no longer recommended for that engine according to Al who had the problem.
 
I have tested 7-8 of their props and there are thousands in the field. I haven't heard of any issues. Maybe at one time they had a bad run, but nothing in recent times or it would be showing up all over the internet.
 
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