Per support request
https://skyline.ms/announcements/home/support/thread.view?rowId=62293
A transition list (that Skyline produced) contains lines for the M+1 and M+2 peptide precursor isotopes. Skyline doesn't understand and throws an error.
These should probably just be ignored, let Skyline's usual mechanisms handle the isotope generation.
See the support request for example files.