Battalion wars 2 fps drops

[slaQ]

** posting here because it wouldn't let me create a thread in games discussion**

Hello readers,

When playing Battalion Wars 2 (latest revisions), I am experiencing fps drops. (both with HLE and LLE audio)
This happens when your character/the camera is facing in certain directions or at certain objects.
However I find it hard to determine what actually causes the fps to go down so significantly. I'm talking from 30 fps to 23 fps.
While at some other points the game will go up to 40-50 fps if you turn of fps limit.

I have tried dx9, dx11, and opengl. Of the three dx9 is fastest, opengl is a bit slower. Fiddling around with the graphic options doesn't do a thing.
Not even a single fps difference. So I'd say that would establish it's not a gpu problem. Rather a cpu problem.
But since it handles the game fine otherwise it's likely to be a simple part of the game that just gets emulated incorrectly or innefficiently.
Like what used to happen with mario galaxy with the backgrounds (I think).

So I'm out of solutions. Hopefully some of you or the devs can be of service in this matter.

Thanks in advance.