Coaxial helicopter CG Point

Hi, I am making a coaxial helicopter and I am testing the drone.
I crashed during the flight test this time and there are some issues.

The first issue is the center of gravity of the helicopter.
I took two flight tests as shown in the log below. In the second flight test, I removed the battery (1.2kg) for a lack of thrust.

In the second flight test, the aircraft took off and crashed.
Looking at the log file was not a vibrating divergence. It was a divergence with a slow frequency.

I simply can’t figure out if it’s a fall due to center of gravity or if gain tuning is less.

1st Flight Test

2st Flight Test