its most likely because you are running f2fs, pls format it to ext4 and you should be good to go
You can always revert from MM to KK without fastboot, just make sure you install proper radio/baseband and should be good to go.
Only KK rom with latest security patch is Racyanos. Give it a shot, i didnt have to block playservices like i had to ...
Thanks, its amazing simple app. Best of all I have used so far. Don't bloat it up like some others have.