Hello

I have a small problem in Illustrator:

I create some text and several logos on a document and then drag the pointer to select them, If I hide them (COMMAND 3) and then bring them back (COMMAND, ALT 3) and try to move them only some of the items I have selected move. This only happens sometimes.
I work in a office with 5 others and it seems to happen with every one.
Is this a bug in Illustrtaor or are we doing something wrong?.
We are all using OS 10.3.3 and CS.

Peter