I don't know if this has been addressed before but I could not find an answer after doing some search. This is how I fixed my Realforce 87UB wiggling left Control key using some Teflon adhesive tape I usually use my mouse. And no, you can't do it the easy way by taping it around the circumference of the stem because you need to get the tape inside in order to fill the gap. I used a Nitoflon tape that has a thickness of 0.13mm.
