I do not think that diet has any thing to do with it. bI'll even there can be two reason of your arm popping out. First that there may be a ligament injury
which was missed previously. This type of injury is called Bankart lesion
. It may be afresh injury picked by you. .so my advice to you is that you should get a shoulder MRI
and see if there is some lesion like this. If yes then you better go to a repeat surgery.