iPhone Footage Glitching Out

For some reason, iPhone footage recently has been glitching out recently both in my timeline and when I render the footage. it is not consistent at all though, will sometimes happen and sometimes not happen.

Here are my Macbook specs:

Model Name: MacBook Pro
Model Identifier: MacBookPro14,2
Processor Name: Dual-Core Intel Core i7
Processor Speed: 3.5 GHz
Number of Processors: 1
Total Number of Cores: 2
L2 Cache (per Core): 256 KB
L3 Cache: 4 MB
Hyper-Threading Technology: Enabled
Memory: 16 GB


Here is a youtube link to the video showing my issue:


Thank you all for your help! Appreciate it!!!

What iPhone model, and what are your video record settings in it?

Machine is a 2017 13" MBP. What version of macOS and what version of FCPX? What codec, H264 or HEVC? In general I'm a little leery of shooting and editing HEVC.

Does this only happen with certain effects? What if you duplicate the project via right-click, duplicate as snapshot. Then load that duplicate project, select all clips in the timeline via CMD+A, then strip out all effects via Edit>Remove Effects. Export that. Does the problem ever happen? If so it may be a 3rd party effect, maybe one which is not compatible with the version of macOS or FCPX you are running.

Does it ever happen if you play the camera clip in Finder before importing it? You can try transcoding the material within FCPX via creating optimized media.

In case it's hardware you can try running Apple Diagnostics. If this finds no problems that's not a "clean bill of health" since the test is very basic, but it's easy to run: support.apple.com/en-us/HT202731

Just FYI, I shoot 4K on 5 different iPhones regularly all the time and never had issues. Wonder if there could be an issue in the phone itself?

Did you ever get to the bottom of this issue? I'm having the same thing happen, also with iPhone footage.

FCP is latest version, Catalina 10.15.3 (which I think might be part of it).

When I do something to change the clips that have the glitches, the glitches move into different clips.

Thanks

Did you try optimizing your media?

No, I don't have the drive space to do it currently. Part of why I upgraded my hardware was so I wouldn't have to use Proxy media so I'd love to find a solution that doesn't involve that if possible. I did upgrade my OS yesterday so we will see if that has an impact, as this issue didn't exist for years and I've only recently encountered it.

I tried to find a way to only optimize the media used in the timeline but ended up exporting off someone else's computer by then. Do you know if there's a way to do that?

You can used the filter HUD in the browser to display only media used in the project. You can then transcode just the used clips leaving out any unused clips. It does transcode entire clips and not segments of clips.

Thank you, that's helpful

So I updated to Catalina 10.15.4 and the issue instantly disappeared. No glitches on the timeline, no glitches in the export.

Lots of beachball and generally FCP not playing nice compared to Mojave, but at least this is gone. Thanks for your suggestions.