Some experimenters see a compile error at si5351.set_correction() in init() at around line 2630.
The signature to the set_correction() method in Jason's si5351 library changed between releases, the latest version includes a second parameter.
#ifdef SP_V
si5351.set_correction(19100);
#endif
If this call throws a compiler error, add in the second argument, as follows:
si5351.set_correction(19100, SI5351_PLL_INPUT_XO);
(Make sure you do this for the selected project, as this call is unique to each project, because every si5351 requires a different calibration offset).