Final Cut Pro X hangs while generating timeline thumbnails

Number:rdar://36421583 Date Originated:2018-01-10
Status:open Resolved:
Product:Pro Apps Product Version:Version 10.4, build 313772
Classification:crash/hang/data loss Reproducible:always
Since upgrading to Final Cut Pro X 10.4, many of my projects freeze FCPX during normal interaction and require a force-quit.

Steps to Reproduce:
* Copy my FCPX library, "Bug Report Library", from [redacted Dropbox URL]
* Open the event "12-23-17 bug report event" and project "bug report project".
* Using a trackpad, use pinch-gestures to change the timeline scale, and two-finger swipes to move around the timeline.

Expected Results:
* Normal FCPX operation

Actual Results:
Eventually (it may take a minute or so), new thumbnails will stop appearing in the timeline as you scrub or pinch around. The preview will no longer update at this point. If you press space to play video, the app will hang / beachball. (See attached hang reports)

Version 10.4, build 313772

Mac Pro, Late 2013
macOS High Sierra 10.13.2 (17C88)
16GB RAM (factory-installed)
Final Cut Pro X Version 10.4, build 313772


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