Running a Ryzen 5!2600 and RX570 with 8gb VRAM and 16gb main memory , have disabled windows defender and all my other antivirus software ( mcAfee) and with all graphics set to minimal the onscreen FPS monitor shows a fluctuating FPS of 19to 40fps which goes up and down in a cycle every half sec of so .., have downloaded xplane11 11.35 from Steam , any advice welcome