Amul / Gcmmf — Fungus in butter amul

We grow up using amul products like milk, icecream, butter, lassi.
we have trust on amul but one incident break my trust on amul.
we purchased butter 1 kg from store with manufacturing date jan 2022
expiry best before 12 month
but unfortunately butter having fungus and smell with black dots on it.
my question is -
why its having 12 month expiry date?
amul is playing with our health ?