New Outlook Randomly Assigning/Overriding Categories to Calendar Items

I use Categories to color code and organize my calendar. In the New Outlook, the system is randomly assigning categories to some of my calendar items.

For example, I have one item that has no category assigned, but now it uses my "Misc Meeting" category. Another one I'd already labeled with the "Analyst Team" category and now it's added "Phone Call" to the item (which is making the wrong color display).

In both of these examples, if I right click to access the categories and correct them (or even just "Clear all categories"), once I submit, after a few seconds the incorrect category labels and colors come back.

Help?