XPlane 11 is running jerky and the running frame rate is intermittant between 7 and 30. OS is Windows 7 Ultimate 64bit and has been running fine previous. No further applications or executables have been installed since the problem occurred. Try re-installing to no avail. 255GB are free on my local drive. Graphics card is a NVIDIA GTX 970. I've tried unchecked all the boxes, set the sliders in all different positions and makes no difference. I'm not overly computer literate so any assistance would be greatly appreciated.