Nether Portals that were synced prior to the update become unsynced after the update, and going from the Overworld to the Nether or vice versa will create a new portal on the first visit through a set of portals.

Destroying the new portal and going back through the original portal links them again.

This bug only seems to affect the first time a portal is traveled through after the update, as no new portals are created when returning through either the original portal or the new one, or on subsequent visits. Quitting and reloading does not affect this.