Hi Vinayak, and all,
I see it's an old one, but for future people like me having the same issue,
POTENTIAL SOLUTION
I got exactly the same issue, PMDG Vcam by Opus FSI
It is the FSX Antialiasing trying to keep up with an unlimited keyframe setting.
After AB testing as much as I could, my solution was to define 60FPS as max frame per seconds.
From there it was all good.
Thx
Wolfgang