Deadshot (the sniper dude) in the bank. I somehow finished it with out him being knocked out or going over to the hostage and it gave me a checkpoint before I could do anything. I didn't receive any credit for it though and the quest marker is still there.
Huh? No I haven't heard or encountered that. I think the way the game reconised flags and how it checkpoints and saves is a bit wonky. I had an upgrade relock on me when I used a fast travel point but it didn't give me back the xp and several people are getting the synopsis unlock early leading to spoilers. It's a little rough around the edges.
Edit: Oh and as Nabs is saying there's a few geometry glitches where you might end up falling endlessly.