I guess you're using Drawing Canvas and filling a polygon with 'convex' unchecked. As it can only really actually fill convex polygons, in this mode it does a highly complex and not particularly reliable algorithm to split a concave polygon in to a series of convex ones, and then fills those all separately. I guess you've run in to the limit of how far the polygon decomposition will go with that process.
I'll increase the limit to 1000 for the next release which might help, but it might run in to other problems, like algorithmic inefficiency with too many points. You may have better luck trying to draw more smaller polygons, or keeping them convex - if you're trying to draw one gigantic concave polygon with loads of points, I'd say that's likely to be a problem.