I recently purchased a Masterkeys Pro L keyboard. The first model I got, I had to return to the store due to the enter key having bad stabilizers as well as space bar ratteling. Then I got another which doesn't have the enter key problem, but it does still have a bit of a space bar ratteling. There is definitely something about the bigger keys feeling different than the smaller ones. I have checked all the keys now and the ones that feel different/rattles are: enter and return, the big + on the numpad, backspace, the right shift.
It's not like they feel exactly bad, but they do seem different, sound different and some of them rattles a bit. It generally feels like it's all the keys that have stabilizers as they are wider or higher.