How about this - Boushh informs C-3PO: ‘Chewie will be outside the exit. Don’t be late’.
Then after Leia’s plan (preferably with gas) goes south, we see Chewie getting thrown in prison and then Han is thrown in with him. This doesn’t allow for the Chewie reveal, but at least it makes some sense. 3PO (and R2) needed to know something about the plan, if nothing more than when and where to leave the building. R2 would already know, but it makes sense for Boushh to tell 3PO at the last possible time so as to minimize the chance of him screwing things up. Of course he blabs anyway, and it’s enough to get Chewie caught.

C-3PO’s dialogue ‘Lando Calrissian and poor Chewbacca never returned from this awful place’ makes sense, since they’re working together. Lando’s the inside man, Chewie’s on the outside.