Big/tall people who returned their Maxis. What did you try next?

I've had my Maxis for a couple of weeks now but still inside the return period. At first all was well other than the quirk of arm rests needing to tilt inwards for skinnier folks. But lately the arms are really loose on the front to back adjustmen at the base. There's no locked in adjustment there. And now, I've started (or just noticed it) to "bottom out" on the backrest right where the curve of my lower spine starts and upper spine ends. To the point it hurts all day afterwards.

I'm 6'7" and 210lbs for reference. I don't know what else to try from here.