i almost lost my sjrc f5s pro plus, when RTH suddenly free fall

the battery was about 25%
but the sky is so clear, after rainy
so i decide to fly beside i want to drain the battery
everything looks good, until the drone warn me that the battery low, about 17%
so i push the 'RTH' button,
RTH looks normal, until after about 15m above the ground i realize the vertical speed (landing speed) is higher than usual
i've found the drone still good, i hope nothing bad happen
do you guys everr have the same experience ? did i do something wrong?

[@mnizar1724]

Kasih lah suara2 backsound biar asik