the second build is officially on 28 inch ELR build

[StoneHendge]

Have you checked that your gas port was drilled properly? I had a 26" R+2 Mcgowan 6 Gr that short stroked. Drove me crazy. Started with a JP LMOS carrier and added a reduced power spring and low mass buffer in it. Didn't solve it. When doing an autopsy down the road, it turned out that the gas port wasn't drilled all the way through. Looked fine up top but the bit never broke fully through and the hole was half the size it should have been on the bore side. Worth checking before spending.

Edit add: A little bit bigger gas port (if yours is drilled correctly) can always solve the problem to. You can always dial back a port with a AGB.