Character swap mods often conflict with one another. If you have multiple mods trying to change the same character slot, the game may crash or display "melted" textures.
Use a tool like 7-Zip to open the .7z file. Locate the .pak File: Inside, you will find a .pak file. JessieBaseAll-599-1-0-1644896907.7z
It acts as a prerequisite for more specific "outfit" mods. For example, if you want Jessie to replace Tifa or Aerith, you often need this base file to ensure the facial animations and body proportions are correctly mapped. Character swap mods often conflict with one another