Can one say:
The restaurant's fantastic dinners had been being prepared by Chef Jones for two years.
By my understanding of English, this sentence does not compute. Perhaps 'had been prepared' works, but this construction gives me the heebie jeebies.
Living in Switzerland as a native speaker, I’ve come to accept the intermittent grammar foibles of the the non-native-well-meaning-yet-sometimes-a-bit-too-full-of-themselves English teachers at my daughter’s schools over the years. But this time the teacher (high school) insists this sentence is grammatically and stylistically correct.