low sample level

[bartek_zgo]

Hi Guys,
I have a strange issue. We are trying to render an animation. For some reason some of the frames have low sample level. I will explain in detail.
I load the whole scene. I set the camera position for current frame. I set desired sample level in session config and start render. I can see the render progress, the SPP is growing and when desired SPP is reached the render ends and I call SaveOutputs(). I do not call SaveFilm() as I do not need it. The first frame is perfect. I change camera position and restart the render. I repeat this procedure many times, and 1 or 2 times for 150 frames I have very Low Sample Per Pixel. The image is very dark with lot of noise.
More details:
- I can see that the render is going correctly. The SPP is growing normally
- After the same amount of time as for previous frame the desired SPP is reached (the render time is the same as for correct frame)
- the only difference I can see, it that SaveOutputs() takes 7s for broken frame and 18s for correct one.

Any thoughts?
Unfortunately at this moment I can not post this frames. When I get the same issue with some test scene I will publish it.

[bartek_zgo]

On question.
I have a loop that checks session->HasDone()
Do I have to call session->Stop() when the render ends and HasDone() returns true?