Tail problem with descent in a mission

ArduCopter Traditional Helicopter
1

When execute a mission I have a problem only when helicopter descend altitude, the tail rotor moves from side to side about 10cm.
When i flight at modes ACRO / ALTHOLD / LOITER not have this problem and also not have problem when i execute a mision at same altitude without any climb or descent.

Logs:

2

That’s true.
I have same problems.