Yesterday I saw this replay in the help room and I don't think this is intended behaviour.
https://replay.pokemonshowdown.com/gen7anythinggoes-736013510
It shows a metronome battle ending because both sides used a single Leppa Berry they started with and endless battle was triggered even though it didn't seem to be one. I also notice mons being in an "endless loop" when they just eat their first Leppa in the official Metronome Battles too.
Ex:
https://replay.pokemonshowdown.com/gen7metronomebattle-736576959
https://replay.pokemonshowdown.com/gen7anythinggoes-736013510
It shows a metronome battle ending because both sides used a single Leppa Berry they started with and endless battle was triggered even though it didn't seem to be one. I also notice mons being in an "endless loop" when they just eat their first Leppa in the official Metronome Battles too.
Ex:
https://replay.pokemonshowdown.com/gen7metronomebattle-736576959