The texture appears to be using 4x4 compression. You can try converting your texture to Nitro TGA using Nitro Paint (using 16-color or 256-color compression), and replace the texture in NSBMD with it.

NSMBe isn't capable of replacing textures with ones that have different compression.
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You need to type the command like this:

apicula convert (NSBMD) --output (folder to extract the converted files)

Just drag the apicula.exe and the NSBMD files to CMD
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