there have been a few, but most have no problems, i believe most problems have been tracked down to two reasons, either the stab had a defect that you didnt detect or when cutting the cover with an exacto there was a scribe made on the balsa and this weakens the stab.you may have but i recommend using a soldering iron to cut the covering.
i have over 150 flights on mine with no problems at all and i think most here havent had any recent problems
hope ya didnt total it !!