1. Base64 decoder fails. See attached file. File from the wild, not is test-created.
2. When attached file is quoted-printable encoded and file is plain text then decoder adds unwonted CRLF.
3. When attached filename not have quotes then decoder lower case filename:
...
filename=IMG2345.jpg
Will be img2345.jpg
I think you can recreate 2 and 3. But 1st bug is real bad.
[I removed the file]