Some players have speculated that the bug could be related to the Demon Hunter class, while others are saying that in general players should just avoid equipping their Templars with shields until they have accepted him as their follower via the user interface pop-up. There are currently a couple of threads on the Battle.net forums regarding this issue, so if you’ve yet to play the game, you might want to read up on the reports (here and here) first to avoid ruining your Diablo 3 experience! Blizzard has yet to release an update to address the issue so in the mean time, avoid equipping the Templar with a shield just to play it safe.