Could anyone confirm that has the Model-D add on pack by 8Dio that the sample Saw 5ths plays the same note I think from C7 and up? Is it a bug? The other samples from the add-on play the whole range of notes.
It all depends entirely on the original sampled material. I don't have the pack in question, but the first pack "The Last Prophet" was sampled on every other note from C1 to C6 if I remember correctly. It can only pitch bend samples up an octave, so what you're seeing is expected behavior.
The sample stretch mode uses a different pitch-bending technique that can cover a wider range at the expense of transposition fidelity and using a single sample across the keyboard rather than a multi-sample, so that might be worth looking into if you're looking for something more extreme.
Footnote: Keep in mind that that I haven't seen my Prophet X in months! It's possible I've gotten some detail wrong, but the basic gist should be sound enough.