I know of NO airplane that doesn't have a quirk, perhaps a potentially fatal one.
I know of no airplane that doesn't have an airspeed indicator.
An airspeed indicator is placed in the cockpit for the benefit of a pilot, who is supposed to use it as a key reference to maintain or change aircraft performance to fit the desired performance for the maneuver being undertaking and remain flying, rather than falling, until back in touch with the ground in a controlled manner. (it is also supremely useful in determining when it is safe to take off and when one must abort a take off, another key performance criterion).
Get back to fundamentals: airspeed.
Root cause: airspeed decay well beyond standards and beyond acceptable limits, with no correction in a timely manner.
Who is flying the aircraft?
Bloggs, if the Company is happy that their flight deck crew are more or less passengers, rather than pilots, then the root cause certainly goes beyond the flight deck crew ... but it raises the question of why that Company remains in business.