A.4.4 KBackup does not work with FTAPE?

Well, there might be lots of reasons for this. First, try whether it works if you disable MULTIBUF support. If that does not help, re-enable it and try playing with its block sizes and also with the block size for writing to tape in the configuration menu. Especially when using ZFTAPE , this parameter must fit the parameter chosen in ZFATPE which is 10240 bytes by default.