The download works fine now. However, i can't verify the problem. Everything works as expected in my tests. But it may be caused by the size of those textures. They are 2048*2048. which is huge. Creating mip maps for these beats requires some memory, because it creates a new image from the pixel data (which is 16mb for one texture alone), i.e. 16 mb pixel data + 16mb image + the scaled instances and the pixel data of those leads to some serious memory usage. Maybe it's running into an OutOfMemory-Exception that somehow gets swallowed by your code leaving the generated mip maps in some in-between state.
BTW: 2048*2048 is pretty huge anyway. It will cause bad performance of the software renderer due to cache misses and it's not cheap on slower hardware either. Consider using a reduced version of the textures.