Frames appear as magenta/black checkerboard blocks 1.12.2

[RedParadose]

Hi, i'm having a real problem with Bibliocraft. Hi, so I added some new custom paintings to the bibliocraft mod file, and i have done this many times before, so i know not to put uppercase letters, spaces, special characters or numbers. Everything was working fine before i put the textures in, but now the textures for the different frames seem to be missing. All of my custom paintings are in the png format, and they show up in the painting press, but all of the frames are showing up as a magenta/black checkerboard block, both in inventory and on a wall. Can someone please tell me what is happening? I tried looking in the textures folder to see if i could find the textures for all the missing frames, but they're not there, and i'm not sure if they were there to begin with, though they must've been for them to show up in game? I also tried downloading a different version of Bibliocraft, but it did the exact same thing.