Plex creating duplicates instead of merging

I recently added a collection of christmas movies and discovered that its finding the metadata and labeling it correctly, but if the movie already exists in my library it just decides to create a new entry instead of merging it into the existing one.

I don’t believe its happened until recently but i’ll have to go through and check every single movie now. What gives and how can i get it to auto-merge again?

Server version: 1.3.3.3148
OS: Windows 10, 1607 (build 14393.576)
Clients, w/ versions, if applicable: Plex Web
What you did? Add movies into plex
What happened? Creates new entries for existing movies when new copies are added
What you expected? To merge existing items like it always has
What are your (relevant) settings?
Link to logs (optional but recommended): https://www.dropbox.com/s/05v72ymvltrrkgc/Plex%20Media%20Server%20Logs_2016-12-18_14-46-11.zip?dl=0

( also posted on reddit yesterday: https://redd.it/5j2y5m )