problem with mip maps level 0 miss on android

Our game have a problem on some Android machine, the setp is:
1.run game.
2.when loading new scene ,press home key ,After minimizing the game and resuming,the texture mips level 0 be miss,I use Adreno Profiler tool see that is black.

but ,if i turn off mips on texture Import setting,it is fine。my shader is very simple, use unlit sahder。

unity3d ver: 4.6.4f1
ANDROID: 4.4.4;
GPU :Adreno405;
CPU:MSM8939;
2GB MEM;

 

I have tried to change the Settings(use 32bit display buffer, 24bit depth buffer, stitic /Dynamic batch,multithreaded rendering ..etc),
but the problem still happen!

 

I'm not very knowledgeable in this realm.
What happens when the mip level is lowered? 10 seems to be overkill imo. Couldn't 4 mip levels be enough?
Is there actual benefit to having mip levels below 64x64 on an entire character sheet?

 

The Max mip levels is automatic generation,I can't control.