Disappointing Max G3 Hill Climbing performance - configuration issue, firmware, or dud unit?

Moments after excitedly unboxing my Max G3 today, I was disappointed to find that the hill climbing performance was much weaker than expected. This is a dealbreaker for me as I live in a very hilly area.

For reference, I weigh 205 pounds, and had the following configuration:

• Vehicle Firmware v1.6.2, Motor firmware v1.5.7
• Sport Mode enabled
• Sport Mode max. speed 28 mph.
• Sport Mode Acceleration Settings Max. Speed
• BOOST Enabled (but not used)
• Hill Start Assist Enabled
• Uphill Hill Assist not available enabled (is it still possible to switch to Global Serial)?

The scooter failed on grades 12%+ (12, 17, 25) for me, stalling out halfway up the hills. I was able to eek by grade 10% hills at ~4mph.

This was surprising to me as I was able to climb grade 20+ hills with my friend's Apollo Go (non-Stellar):

• Apollo Go has 1500W dual motor vs 2000w single motor on the Max G3 - my research is that for hill climbing, only total wattage matters and # of motors doesn't actually matter as much, but I may be wrong here
• Both these scooters performed similarly on this reviewer's 23 grade hill climb test, bottoming out at ~4mph but both making it through) (Apollo Go, Max G3).

Has anybody had a similar experience? Is there anything that I can try to remedy this?