I’ve been developing GP on 4.4 for a little over a month now. The theme and add-ons are always being built on the latest beta version to make sure there’s never any compatibility issues.
This site is on 4.4 as well with no issues.
My guess is you’re using a plugin that has compatibility issues.
Try deactivating your plugins before updating.
Also check each plugin forum to see if others are having the same issue.
Let me know 🙂