I haven't tested it yet, but looking at the code this seems to have the same bug as
https://github.com/apprenticeharper/...ls/issues/1828 :
When parsing the encryption.xml, you need to manually check for each entry if that's related to AdobeDRM or if that's something else (like font data). And after decryption, you should only delete the AdobeDRM entries from the encryption.xml, and only delete the whole file from the EPUB if it's empty (no other entries that aren't DRM).
Otherwise this breaks embedded obfuscated fonts (which are also included in the encryption.xml).