A test aircraft experienced an uncommanded pitch up or down event, eerily similar to the 737-MAX fiasco. This is said to push production out until at least 2024:
The Boeing 777X is allegedly facing serious certification issues, and it’s now unlikely any of these planes will be delivered before 2024.
Source: Uh Oh: Boeing 777X Facing Certification Issues | One Mile at a Time
The FAA is now keeping a close eye on Boeing as Boeing has lost the confidence of regulators after the 737-MAX disasters.