Maybe a different spatial filter? Overlaps instead of contains?
@cjones28
I do that and it works like a charm. Except I use "initiator intersects result" rather then inside.
Make sure your projections match, of course. A reprojector on your initiator if needed.
Bufferer is ok, but I would then use a boundingboxreplacer on the buffer result as I understand it to be a circle. (check the capabilities file)
Or use "Boundingbox Intersects Result"
edit:
I tried it out by replace my grid by circles based on their centerpoint. This results in blank (white) results.
So it is the circular buffer that causes it.