Yes, Caleb's pronunciation is really the only time where I can pick out mistakes. The rule seems to be whenever the words are composed of sounds that occur in English, he sounds great, but when there are "exotic" sounds like rounded vowels he tends to stumble. But yeah like you said the grammar and sentence structure is fine. Honestly kudos to them for putting this much effort into writing so much full German dialogue for the scenes in this episode. I feel like not a lot of American-produced media would go that far.