Telling a Companion to return to where you found them or to the Lucky 38 from Caeser's Fort always results in them getting stuck at the gate, since they can't take the raft back to Cottonwood Cove (I think that's the place?). I've now tried this with two different companions and it happened to both. They never reach the Lucky 38, but if you talk to them, they'll act as though they're standing where you first picked them up.

This can really unfortunate since you aren't allowed to bring a companion in to meet Caeser.