Very strange autopilot issue. Occasionally when I turn the autopilot on it will not respond to NAV or HDG. ALT works fine. This has happened three times out of maybe 50 flights. Not a huge problem but it's impossible to continue a Vatsim flight. It seems to happen mostly if the system is under a load from a scenery add-on or other programs running.

 

Anyone else had this problem?

More on this issue. I have found that if I am running a VA program the A/P will not work either in HDG or GPS mode. It does work in ALT. One of the VA's I belong to is MEC (Mirage Virtual Charters). The monitoring program you run for them is called VAFS. If this is running the AP will not work. I thought that maybe this was a fluke but I found out that if I am flying a flight for Pilot's Edge the same thing happens. If I am running their program no AP in HDG or GPS. I use the GNS 530.

 

It's a mystery!

I found out what the problem was.  It was a memory problem.  I solved it by adding 8 more GB to have 16GB.  I have never had a program do something like this before.  Usually you will get some kind of out of memory error if you have a memory problem.  In this case when I had a lot of applications running some of the functions of the 850 just stopped working.  It happened about 60% of the time.  Since I added the memory everything has worked perfectly.