I noticed my TV Shows stopped syncing. Upon digging into the code and comparing it with the XML from the Plex API, I found that "year" was undefined in newer media. Looks like it was changed to "parentYear".
In the release code, I was able to fix this by changing
year = _ref3.year ;
to
year = _ref3.parentYear || _ref3.year ;
in node_modules\plex-sync\lib\plex.js.