i don't think this is a bug, you should just be able to get away once he's on the phone. you might try a different control method for a few minutes, like a joystick? see if you can get through using that. i had a problem years ago playing the game where manny wouldn't climb to the roof in year one to get at the pigeons. i tried the joystick and he went straight up. weird, i know. might be worth a try.
if you can get close enough to the ladder and get manny to look at it, pressing use / enter will make him climb, even if he's a few steps away from it.