I replaced Faythe with Garret for a short while; mainly to test him. Now that Faythe is back in my party she can't pick locks or steal anymore allthough her skill lvl is high enough. Both skills are on lvl. 8 but she can't pick the lvl. 5 lock in Hydroponics (yellow) - Airlock for example.

Did you assign her to these skills in the party management screen?

Damn. Now I feel stupid. No, I didn't reassign her. Thanks for the help.