Is the "porpoising" still a problem, detected at first flight?
Yes. The aircraft is inherently unstable. This has been addressed by an Stability Augmentation System, which works very well. But, lets be honest, it ought to be; its only an autopilot at the end of the day. However, in principle, it is only papering over the cracks. No large aircraft should have to use an autopilot to maintain straight and level flight. If the SAS is not working, the continual demand on the pilot becomes unacceptable; hence the need for the system.