How to I tighten my Bandai D-Arts Mega Man X joints?

My action figure has loose elbow and knee joints. The knees just flop around making it really hard to pose him. His right knee was floppy out of the box, but the left one started stiff. His forearms are able to be removed in order to swap between his hand and X-Buster. However, the forearms and buster keep falling off of the elbow joint. If it helps, I believe that this is a fake version because the neck is not painted and the real version is said to have tight joints.