The sketch is now wrong. Doh!
I just checked the library details again. They have changed the way calibration is done, it now has a one time set " si5351.set_correction(value) ; " Looking at the sketch now.
Your problem about going back is that the new library v2 persists in your Arduino/libraries and needs the SI5351 Library folder deleting from there and then add the old library again in the old sketch.