Strange problem! I have several missions with the F18 “saved”. When I load some of the missions the A/C come in with the AutoThrottle on, which make the a/c scoot across the landscape till I can get the brake on and turn it off. Other missions are OK.
Have ensured the AT is off and “resaved” the mission, but to no avail? Suggestions?

I was recently advised (for a different payware aircraft) that loading then immediately reloading the saved flight would clear up a certain problem I was having. I don't know if this will help you but I can't see any harm in giving it a try.