1. What is the reason for the white LED sparkling or flashing while flying?

There are three possible reasons: First, compass calibration fails. The white LED flashes or sparkles especially when helicopter is rotating. Second: Helicopter's attitude is not suitable to switch into auto-mode. If the helicopter is flying without hash movements, it may result from the vibration due to the improper adjustment of the helicopter's mechanics. Third: After some hash movements, there are some errors while calculating attitude.

2. What's the reason for helicopter's drifting after switching into auto-mode?

If helicopter drifts slowly only in one direction, it is possibly resulted from moving some sticks accidentally when the user switches the helicopter into auto mode. This is always caused by some input of a stick when switching into the auto mode. An easy way to deal with such situation is to release all sticks and switch to manual mode and then switch back into auto-mode quickly.