A dataflash log is preferred instead of a tlog.
For stabilisation, you need to check all the directions are right in a hand-held test, with the sticks neutral:
* when in QSTABILIZE mode, roll the vehicle right. The right motor should increase thrust, the left motor should decrease
* then roll it left, the left motor should increase thrust, the right should decrease
* then tilt the nose up. The rear motor should increase thrust
* then tilt the nose down. The rear motor should decrease thrust
* now rapidly yaw the vehicle to the right (so nose goes right). As you start to yaw it, the right motor should tilt forward, the left motor should tilt back
* now rapidly yaw the vehicle left. The left motor should tilt forward, the right should tilt back
Then do all the same tests, but on without holding the vehicle, instead have it on the ground, and use the sticks. Use a small amount of throttle, but not enough the take off. Check that as you use roll, pitch and yaw that the motor outputs are trying to move the vehicle in the right direction.