1. What the circumstances were.
Had a drifter, Speedy, joining the colony from a charity quest. No other special circumstances. I'm assuming that whatever went wrong did so at the moment she joined, but I don't have a save file from that time.
2. What happened.
About two days after joining I wanted to change her clothes due to bad weather and realized I can't. She dropped headgear and a t-shirt, but the jacket and pants are locked.
3. What you expected to happen.
This is not the first time I had a colonist join from a charity quest, but I was always able to change their clothes afterwards. This is, however, the first time a colonist joined in this playthrough. I attempted to change the outfit settings, so she would drop them herself, but it didn't work. I couldn't find any workaround.
I do have few mods, but none of them related to clothing/appearance or colonist behavior.
Attaching save and log files.
Thanks for the bug report. I will work to reproduce this in my own testing, though be advised any mod can cause bugs on anything, I have had people swear their issue isn't caused by mods, their mods don't seem related at all, but still find its a mod doing something.