I've attached a video of an issue that I'm having with a blank space on the timeline.
I've done everything from trashing prefs, rerendering, restarting etc. When I was doing this, I remember trying to undo and it was unrecoverable. I also looked at the edit menu and it said Undo "Circuit..." I think the next word was "breaker"? Not sure but definitely remember the word circuit and wondered what the **** that was. Anyway, watch the video and hopefully this has been solved.
Did you turn off background rendering, then delete all render files, and reboot your Mac? But yeah, I've seen that before, a VERY long time ago. Did you try opening a backup? What macOS and FCP versions?
Yes I opened up a back up but it was quite a few hours old so I had to come up with a workaround.
What I did was copy everything before the missing clip and pasted it into a new project. The did the same for everything after the clip. I reproduced it again, but didn't record the steps as I was just going through workflow.
As for what you suggested, yes I did all that. Still no fix.
Do you suggest that I work with background rendering off moving forward with all projects?
I saw this a few times on a large project late last year, cause unknown. It is apparently some kind of corruption in the SQLite database for that timeline. Each project (aka timeline) has its own database.
I think I tried the undocumented project repair command, OPT+Clip>Verify & Repair Project (project must be loaded first). That didn't help. I either exported a project XML, then re-imported, or else I just opened a previous project snapshot before it happened and manually re-did the edits. I can't remember which.
Obviously I also did all the normal steps such as reset FCPX preferences, delete all render files, etc. None of that helped.
I had multiple audio lanes which had various versions of a music performance. I think I isolated which one was the problem by disabling them in sequence. IOW pressed the V key on the visible part of each one, then played the non-visible part to see if it went quiet. When I found it I deleted it from the library, re-imported and re-added it. It was definitely frustrating.
I never saw it before or since, even though I've worked on very large projects. This was on a Vega 64 iMac Pro, whatever the current version of MacOS and FCPX were in Nov/Dec 2019, all media on locally-attached Thunderbolt RAID formatted HFS+. I had a lot of mixed 23.98/29.97 frame rate material and used optical flow rate conforming a lot, plus Neat Video a lot; not sure if that was a factor.
First back up the entire library. This is easier if using all "leave files in place" media and if the cache and proxies are external. That can be done using the library inspector Storage Locations>Modify Settings>Cache and Media settings. Provided you don't have internal media that makes the library very small so you can easily duplicate it in Finder. Then make a snapshot duplicate of the project, rename it something unique, export the project XML, create a test library and import that XML. See if the problem is still there. Sometimes the translation process of internal database to XML and back will filter out some problems.