They broke it.

Final Cut Pro is a great program, but this version is AWFUL. I’m sitting here trying to edit a video in 10.2.3 right, theres a clip I need to speed up, and with the preview set to “better quality”, 0 frames are dropped. Now upon updating, the same clip from the same project drops several frames, even in “better performance” mode. It is not my machine either, I have the highest end 5K iMac (quad core i7 6700K, 32GB RAM, AMD Radeon R9 M395x 4GB GPU). I had to go back to 10.2.3, it works, its smooth and it doesnt drop frames. I really hope Apple fixes this as I do like the appearance of the new Final Cut, just the issues it has are unacceptable.

-DaSamNudge

DaSamNudge about Final Cut Pro, v10.3.1