Don’t try to make your unpredictable dog something she is not.
I often hear stories about dogs who used to be sweet, but “suddenly” turned into aggressive monsters. People understandably want the “old” version of their dog back, but that’s not something that any dog trainer can promise.
First, dogs don’t change suddenly. The behavior usually starts small, but humans miss the signs. Sadly over time, the issue snowballs.
Having an unpredictable biting dog is like having a child with autism. You are working with the autism, just as you are working with the biting. Yes we want the biting to stop, and mostly we can stop it, but there is ALWAYS a level of management required in order to keep everyone safe.
Always honor the dog that you currently have, rather than wishing for the “old” dog to return. Most importantly, keep your expectations realistic.