If it were mine, I’d remove the brake, check torque/ assembly items, and probably swap scopes for a proven performer just for shits.
I’ve also had more than a few barrels that took a couple hundred rounds to foul up and settle in before producing groups in the range that I would have expected.
Lastly, and this is admittedly a sample size of one, I’ve had four Grendel barrels in the last five years - Lilja, two LaRue, and Ballistic Advantage - none of them were solid sub-MOA performers for me on paper at 100 yds. While there are certainly examples of barrels/ shooters out there that are sub-MOA capable with the Grendel at 100 yds, I don’t think that is where this caliber shines. It seems to me to be much more capable at range on steel, and since that’s something that I don’t have a lot of access to in my neck of the woods, I retired my Grendel attempts and stick with .223 for punching paper.