I have same problem. It happens randomly. When I look up to the sky fps becomes normal but when I look at ground it continues. After 1-2 minutes it backs to normal.
After several A2G attacks I noticed WPDSG not working. This was also happening before the this week's patches.
I can see the diamond on HUD for 0.5 second then it disappears.
I fired all AIM9Xs but still have that seeker circle in every AA weapon modes.
In that pictures you can see I choosed amraams and guns but seeker still exists.