I'm not sure if it's a Corona or Forest Pack problem, but since I've never run into a similar issue with Vray+Forest Pack combo I decided to post it here.
The problem is that random frames in animation seem to loose Forest color/tint information. It affects all forest color maps in the scene. Below I attach 2 consecutive frames - first one is ok, the second one lost given color tint.
The error is completely random, it does not appear every nth frame, etc.
Corona 1.7, 3dsmax 2016, Forest Pack Pro 5.4.1