m16 R1, APU STAPM throttling after 30 minutes gaming

Alienware m16 R1, AMD R9 7845HX, RTX 4080, TCC set to 85 °C

After 30 minutes of playing Battlefield 2042 (max settings, ~78 °C CPU Package), the CPU drops from ~80 W to 30–35 W due to the APU STAMP Limit reaching 100%, making the game unplayable. FPS drops from 120 to stutter, unless I cap at 90 FPS.

Oddly, Cinebench R23 runs for 10 min at ~110 W with STAMP only ~40%. Fans work fine, surface temps aren’t excessive, and latest BIOS/drivers/AWC Performance mode are in use.

From my understanding, STAPM is meant to protect chassis temps, but this throttling seems overly aggressive given the thermal headroom. Is there a way to adjust the STAMP threshold or is this fixed firmware behavior?