Prarm: motor interlock enabled

Hi, i’m confused that this message appear when arming, as both ch8 option and ch7 option is do nothing.
Refering to drones-discuss, i sure don’t use motor interlock feartue, but this message is still appear when arming.

It’s very strange problem. So, anyone can help me?

Some detials about my configuraton:
Firmware version : APM: Copter V3.5.2 heli
Hardware : PixHawk2
Configuration : CH8_OPT 0
CH7_OPT 0
ARM_CHECK 0