Respected Enemies Glitch?

[Cody]

Alright, having trouble getting this Achievement. I have Marburg's Dossier at 100% and have him at 10 friendship. At the museum I went to deactivate the bombs and picked all professional options when talking to him. At the end after the shootout I, again, picked all professional options. I never got the option to let him go, instead he ran for it. Thus I never got the achievement. What gives? I am pretty sure I did everything right(I mean he was at 10 Friendship and his dossier was fully complete)so whats up? Is anyone else having this problem?