Almost.
It's not "unstable", it's just "different". But the system pretends it's not, until it fails. Even if it fully failed, the pilot should be able to fly the aircraft. But if it fails, and the pilot was either told "this aircraft is the same", or is attempting to adjust it by the system thinks "I know better", then the two conflicting inputs are a problem (or the one conflict and it nosedives).
They either needed to re-train/certify the aircraft, and avoid most of the problems, or make the system much more robust so the problems/faults/conflicts almost never happened.