I have ED-E as a companion, but while I value his assistance in the open terrain, I don't like his behaviour underground. So when I went to explore Vault 34, I left ED-E at the Lucky 38 apartament, telling him to wait.

To my suprise, when going from one area to another in Vault 34, ED-E suddenly appeared, his behaviour set to following me.

While it looks strange, the thing I'm worried about is the thing I remember from a un-finished playthrough from 2 years ago, when there was some but rendering ED-E stuck in Vault 34 if I remember correctly (though that was an earlier version of the game and the bug was possibly fixed since then).

Anyone had this? What causes this?