The rattle is an indication that the inner wall of the bat is breaking apart. This will eventually happen to almost all of the composite bats as they go through their life cycle. The fact that it has happened with the one year (I assume) warranty period is an issue. Return it. The danger here is that the bat could break apart when hitting the ball and a large piece of bat with a jagged edge could be flying around the field.
As to passing inspection, some umpires are more vigorous than others in shaking bats and listening for rattles.
Rattle does not mean wall is breaking apart. Could easily be epoxy from the end of the bat that broke
off and now is rattling around in there.
There could be multiple reasons for rattling.
I would not return it until your warranty period is coming close. Some umps need to relax and educate
themselves more about bats.