Maybe You Accidentally Changed The Image File Types, For Example If You Open Preset_4.material In Note Pad You See It Shows The File Type .png Or .jpeg ~ ect.
Make sure you're images are that file type.
You Could Of Also Changed Something In The .material File? If So Make Sure The Preset_5 Is The Same But Not The Number Of Course, It Should All Be The Same But Number 4
Did you try make a left and right side? i had problems too, make sure if you downloaded it you overwritten the .material file, or it's the same or it won't work,
Make Sure The Images Are All The Correct Size, It Will Tell You How Big In The .Material File
Also How Does The Preset Show Up? White? See-through? Glitchy?
Anyways Try That And Let Me Know