A middle piece mechanism is loose. What do I do?

The middle piece of the blue side of my Rubik's Cube is unusually loose (but still attached), meaning the blue side turns far more easily than the other sides and, if I try to solve the Cube at my preferred speed (fast enough to solve in 1 minute), it's unusually easy for a piece to pop out.

Taking off the edge and corner pieces reveals that, unlike the stable center pieces, the center of the blue side can be tilted side to side and pulled maybe a few millimeters away from its normal position.

My Rubik's Cube is still usable, but I prefer not to until the blue center piece is secure again. (I'm aware of how to remove corner and edge pieces and put them back on. However, this problem is with the mechanism itself. Again, not fully detached, but uncomfortably loose.)