MP-44 Optimus knee repair?

[Magnus]

So I was posing my MP-44 and decided to bend the figure's knees to create a kneeling pose, but then I noticed that the left lower knee joint seemed to have a lot of 'play' without the ratchet joint engaging, and the blue tab on the back of the knee wouldn't move into its slot. Meanwhile, the right knee was fine.

Unsure as to what was going on, I decided to dismantle to right knee to see what it was 'meant' to look like. i only disassembled the three screws at the knee joint itself - the silver-blue one and the two black ones. I then reassembled the right knee and did the same for the left. Not seeing anything substantially different, I reassembled the left knee, but now both knees seem to have the same issue. Also, I noticed that the larger of the two black screws doesn't have a 'stopping point' when tightening.

Has anyone else had this issue with play on the lower knee joint of their MP-44? Also, has anyone attempted this knee fix, which is sanding down a blue post in the knee and lubricating the joint, or even just the lubrication? I know about gluing the part with the tab, but I'd rather not do this.