When you say "Use the command line "unltfs" command to clear a tape:" you don't mean on one of my good tapes with all my data surely? Do you mean with a blank tape?
I tried the command with a blank tape and it throws back this message:
dyld: Symbol not found: _UCNV_TO_U_CALLBACK_STOP_4_0
Referenced from: /Library/Frameworks/LTFS.framework/Versions/Current/usr/lib/libltfs.2.0.0.dylib
Expected in: /Library/Frameworks/ICU.framework/Versions/Current/usr/lib/libicu.40.1.dylib
Is there something missing from my Library?