2017 Ram 2500 Cummins P0729 Code: Transmission Ratio Error During Downshifts

I own a 2017 Ram 2500 Cummins with a 68RFE transmission. After recent modifications—including deletion, tuning via EZ Lync with advanced transmission profiles, and exhaust upgrades—I've started encountering the P0729 diagnostic code, which indicates an incorrect gear ratio in 6th gear. The issue only appears when downshifting from 6th gear during passing maneuvers—typically under 25% to 40% throttle. The vehicle shifts smoothly through all gears when starting or cruising, and even performs well when downshifting due to speed alone. However, the P0729 code triggers specifically during aggressive downshifts for passing. I've reverted to the original tuning file provided by the tuner, but the problem persists. Is this a known issue with 68RFE transmissions? Could it be caused by improper tuning settings or a faulty sensor/equipment in the transmission system? Any insights or experiences from other owners of similar vehicles would be greatly appreciated.