I am missing something here, my app when in Debug conf can access correctly the sdcard but if just change it to...

I am missing something here, my app when in Debug conf can access correctly the sdcard but if just change it to Release mode I get access denied. I've double checked my permissions and can't discover the issue.
Besides the Uses Permissions, how could I know what really is missing?
This is the 1st time I face such problem.