I remember MX Red switches were difficult to get in 2012.
I, too, found three MX Red keyboards, CMQFR/Filco M2/Corsair K65, I owned were the key switches felt scratchy to me.
I would think it's a of the MX Red switch. I gave up on them; they required too little down force for me and I had too many
accidental key strikes. I'm rather heavy handed and I rest my fingers with slight pressure on my keyboards.