I'm not sure if it was intended to make it more challenging or if it's a bug of some sort but I gotta say it's very annoying for me. Anyone else notice this?
Yep. I did my share of lockbox robbing before the update came out. It always pulls you out of sneak. However, they designed it so all guards/shopkeepers walk away from chests from time to time to give you a window of opportunity. I agree it is very annoying.