"Looked your video. I'd say it's the ESC's are the problem. Might try Autotrim. Or get different ESC's.
I use the Qbrain 4 in 1 25A. Real simple."

"Couple other items. Test Alt Hold first before Loiter. AltHold needs to be close and working. This proves your copter is stable. Start in Stable mode, then switch to AltHold. If that works and your compass is right then Loiter should work. But be…"

"APM does have autotune. Channel 7 option in the parameters. Enable ALThold then switch on AutoTune. But your copter needs to be stable to start with in order to complete the autotune.
I'm a total noob and this is my first build. But I have mine…"

"Found it. Thanks search for quadcopter ebook and it's the first link."