I have this problem as well I believe my client was corrupted during DL and my windows are smaller then everyone else's.
I am so glad I am not the only one with this problem. Every single time I try to jump through a window, it fails and the enemy usually sees me struggling to get through and laughs at me then kills me. So you just sprint, jump, and crouch? I tried that! Many times! I gave up trying to jump through windows a long time ago though when they nerfed the window size on towers. I may try to get into it again but I don't know, I still have nightmares of enemies killing me as I am trying so hard to get through the window. They really should make tutorials for this crap.
yeah, I've died quite a few times trying this advanced maneuver as well, but not as many times as me trying to scale the outer walls of amp stations. Almost every time I got shot in the back, or someone would walk up on top of the wall and shoot me in the top of my head