Saab are infamous for having marvelous engineering concepts, that fall down short on practical durability and cost.
Everything I've come across about their variable pitch prop systems says the same thing. Great concept, if you can afford to keep it in repair
and finctioning over the years. Otherwise it falls into the category of "moving parts located where you can't access them, in a corrosive environment with no spares to be found within a thousand miles".
If you've got it, enjoy it. And if you've got lots of money, call Saab and ask them to sell you a kit of spares if they are still available.