I have used Preview to create a number of annotations for a PDF file. The annotations are a mix of boxes, ovals, text, arrows, etc…
Upon exiting and reopening Preview, it seems to have lost the majority of the annotations. Many of them still seem to appear in the Inspector's panel for annotations, however, the text is missing from most and many other edits are missing.
I've also tried recovering an earlier version of the file using Time Machine, and restarting the computer, but all versions past or present display the same corrupted / lost annotations.
OS X El Capitan 10.11.2