Idk if this is a bug regarding companions in towns, but I have found the same issue. The first companion can't recall the other comapnions in towns.
I found that most of your companions will be in the town tavern instead of the streets. And if you head in there you can call them all out.
I noticed other people have this problem but with a 1.5.7 save.
I started a fresh 1.5.8 and reached the part where I have to talk to Istiana or Arzagos. I head to their door but can't enter their house. They also don't appear to be in town and have "Never been seen before" in Encyclopedia.
I guess that would make sense. It does sound exploitable ... I think?
I thought it was a bug.
I just recently won a "Sally out fight" it was my troops and my garrison vs 6 enemy lords. I captured 3 of them but the other 3 are in ym dungeon and I don't have access to them. I assume they were captured by my garrison?