May I ask how long it takes for this to occur? Minimizing doesn't seem to matter on my end, but there could potentially be color precision issues after 2 or 3 hours for the NTSC effect, because the frame counter is unbounded. I would try replacing this on line 605 of CRTFunctions:
_frame_acc++; _frame_counter = _frame_acc div max(1, floor(game_get_speed(gamespeed_fps) / 60));
With this:
var _div = max(1, floor(game_get_speed(gamespeed_fps) / 60)); _frame_acc = (_frame_acc + 1) mod (32768 * _div); _frame_counter = _frame_acc div _div;
Let me know if that works out, and I can update the pack if so!