PMDG 747-400X Problems during mid flight

The last few times I have attemted a long flight with my pmdg 747-400X, it has done the weirdest things. I have double checked my FMC and pre-flight setup to make sure everything is right. Read the manual and view several video tutorials . I started a flght from EHAM to KDEN. The first several hundred miles everything is fine, then all of the sudden the plane goes into a type of holding pattern. Then it will lose speed and stall out. I have to disendaged the autopilot and reset everything. It keeps flying around in a circle then stalling out. Anyone else experienced this?

Did you complete the INIT REF page especially entering your POS ?

I would select to fly to next waypoint.

Yes I did. I read the manual and followed the tutorials to a T. Another problem with the FMC is it won't delete way points.

It doesn't delete it, you must select the next one and enter into the previous.

For a starter you can't avoid manuals. Afterwards you can, I don't read these much but when I started (it was a PMDG 737v1), I printed out the whole thing and read it 10-20 pages aday before going to sleep. I skipped some info (10-15%) but the theory and especially the FMS operation I've read 2 times start to end, then I still had to read some sections another 10 or 15 times )))))

I've got the PMDG 747X Model, and I don't have those type of problems during any of my 3000 to 12,000 mile flights just so ya know .

Well, it wasn't doing this when I first got the product. Then it started. I used to be able to complete flights.

What about

-route discontinuity cleared

-bad trim, in my case, my ariane b737 looses autopilot and does exactly the same as you.

-did you check whats programmed on "hold" key ?

- winds, fuel, altitude ?

I just flew the PMDG 747X from KLAX to PHNL no problem. Trim is fine as is route discontinuity. I'll have to try it on a flight that is 4000nm+ and see if it holds.