Hmm, that's an odd one.
Usually, when you start your script up, drag the actors from the left hand side into their assigned roles, then drag them from the boxes in the middle to the coat hanger to assign costumes, they hold that costume set for the whole of the movie. Is this not happening?
Alternatively, if you're using extras or other stars off your actor tree that AREN'T the principals, if you drag them directly off the tree onto the coat hanger, set their costume and then pull them into a scene in your base shooting script, it will sometimes reset their outward appearance to the "default costume set" for that scene.
Provided you've set their costume in the initial window as mentioned above, you can drag the actor/extra across from the tree on the left (NOT from the scene itself) onto the hanger again in the first scene; they should appear with the outfit you assigned to them again. Click the tick to impose that on them once more and they should then keep that outfit on throughout the whole script; it's an annoying niggle.
The mannequins always reset if you don't put at least one scene with all of your principal stars in it into the shooting script (had this happen to me a coupla times when rejigging things; very annoying).
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