I have no idea on where I should start debugging this issue. I have not made any changes to the character blueprint of c++ class and it was working fine until I encountered a crash in unreal engine 4.9 (messing with an AI c++ class) and now whenever my player crouches, he is no longer on the ground.
Okay, I solved this by opening up the animation in persona and clicking “Show advance options” and switch the option for the hips to “Animation Relative.”