У вашего броузера проблема в совместимости с HTML5
I'll walk you through setting up Servo Tilt and Channel Forwarding. If you need more than 2 channels, use Channel Forwarding. Otherwise Servo Tilt works fine.
https://github.com/betaflight/betaflight/wiki/Servos-&-SERVO_TILT-for-3.1
"This means that you can not use Output 5 and 6 for servos."
https://github.com/betaflight/betaflight/wiki/CHANNEL_FORWARDING-for-3.1