Thank you for the reply, yes the corrective action you recommended is actually what I did earlier in an attempt to discover more keys affected. I opened the case twice this morning as a result of that, frustratingly a new key will become defective after Ive already put the case back together! haha
The modules under which I removed the loose pieces of plastic feel completely normal and have no detectable faults (by feel and by the leyden jar diagnostic tool) so Im deciding to leave them in for now. I guess Ill know if I really need to replace the module if the same ones fail repeatedly.
I thought I was pretty careful during keycap installation, I only applied as much force as necessary to install each one, but after finishing, I noticed many of the keycaps resting at different heights, I know its not the modules themselves as I inspected them all pre-installation to ensure they were all uniform in appearance, looking from multiple angles, pressing each one, etc... For the more egregious caps, I pushed them in a little more to get them more in line with the other caps. These modules definitely required more force than the others to have the keycap installed. There were only about 2-3 modules whose stems felt like they fit the keycap like a glove and required no force. Im assuming the factory that made these had some sort of tolerance for the dimensions of the stems, and similarly with the keycaps, and the slight variances resulted in some keycaps needing a more forceful install.
For the rest that are still higher than the others, Im hoping that days of typing will eventually move them down little by little. Im about to open the case for the 3rd time today now that Im finished with work and given the entire board your recommended mass press treatment (hopefully 8 hours of typing will have helped dislodge the rest of the pieces I havent discovered yet)