Ohhhh Boy , this doesn't sound fun or good !!
Can only imagine how much time simmers are spending trying to figure out the issue / problem ??
Just wait until Prepar 10D and or Prepar 25D comes out ,,,,,
I'll just stick with my 1950's Flight Sim Computer , it, Worksssss !
Was reading all these issues & problems over at Just Flight forum with users and their Aircraft
Those having any issues may want to read up and stay informed with issues regarding Prepar4D
LINK : http://forum.justflight.com/forum_topics.asp?FID=69&title=prepar3d