yah efpse cannot handle anything special characters in your filenames whatsoever
no underscores, no spaces, nothing but a to z and 0 to 9. anything else will crash.
if you get your textures from an asset pack and they have filenames with underscores or other characters efpse doesnt like, there is a free batch renaming program, https://www.advancedrenamer.com/ that i have used that makes it alot easier to import your textures to efpse, and not have to rename every texture individually before import.