2D Sprite leaves a trail when moving diagonally

Hello! Sorry for my poor English!

My problem: I'm trying to diagonally move some object with large speed. Move script taken from this tutorial. Quote from it:

 Vector3 target = moveDirection * moveSpeed + currentPosition;
 transform.position = Vector3.Lerp( currentPosition, target, Time.deltaTime );

My example sprite is:

And i got move effect like this:

I can't even catch it on a screenshot, so i forged it in Paint:) This occurs in build for PC with any quality settings (but not in Unity Editor!) and also on Android Tablet. When I slow down move speed in script movement is fine perfect, there no blinks and trails, but it's not acceptable for me. When I move object straight, not diagonally. It's better, but not good either. In the project from tutorial I can set any speed and there is no such effect. I tried different options of sprite's import (filter mode - point, bilinear, pixels per units and so on), but no luck, bc I don't actually understand what i'm doing.

Help me please. Thanks!