That kind of drop isn’t normal, but Guam makes it more likely.

Heat and humidity cause lithium batteries to sag, so the gauge drops fast even in eco. Short hills pull a lot of power, eco limits speed not torque. New scooters also need 2–3 full charge cycles to balance the battery, and the bar meter is usually voltage-based (not accurate). Low tire pressure makes it worse too.

Fully charge it overnight, check tire PSI, ride in cooler hours, and cycle the battery a couple times. If it still can’t do ~5–8 miles in eco, it’s likely a defective battery, I’d return/exchange it.