Linchimb

Thanks Hulk and Bill. Yes the other side has a square metal plate which holds the bolts in place. The spring is also attached to this part. And the belt also fell off...I put  all of them back on now! hopefully this won't cause any issue in using the wheel

Thanks everyone for your kind advice and suggestion. I tool the blue cover off and noticed that the square metal plate, the spring and belt were all loose. I put them back in place and hopefully the wheel will be working again!