Sorry to hear so many problems with Spectre. It is working for me fine now, uploading samples without converting them to MIDI first. Selecting MIDI in as Blofeld was the trick (the instructions all tell you not to, but that’s what works for me). Using Blofeld OS 1.25, Windows7. This allows me to only upload new/missing sample programs to a sample set, while also keeping the already uploaded samples on the Blofeld.
EDIT: the video I linked above, as well as this, helped me figure it out. https://modulatethis.com/2014/12/15/must-read-waldorf-blofeld-synthesizer-new-1-23-firmware-blofeld-new-spectre-app-secret-sauce-sample-transfer/