Created Unassigned: While copying template Locked cell which has image gets unlocked [14924]

I'm copying the template which is already locked some of the cells..

In that, I gave workSheet.Protection.IsProtected = false;

Then i've inserted cells. and locked those cells. and then I've applied protection. Now Locked image which was copied from template has unlocked. But text cells are locked. why is this happen ?

What I've to do to solve this ?