CX20 ESC MFL1218 V1.3 won't keep calibration

Hello, I’m a newbie and learning the hard way i would really appreciate if someone can help me out!! To make it sample here’s the link to the video that describe my problem! I hope i don’t violate any forum rule by doing so and if yes i really apologize. I have search entire forum and web and no answer so i really hope you can help me on this thank you.

Arducopter APM 2.8
Firmware v3.2.1