Premiere Pro Glitching Videos in Preview and Export - Source Footage Fine

So after speaking with the Adobe team I finally got this sorted out. I, like you, am using iPhone footage and it is this that is causing the glitches.

I was told that the format of the HEVC footage (iPhone footage) causes Premiere Pro to drop frames and put those glitches into the footage even though the raw footage is fine. These glitches, although you may be able to temporarily remove them from the timeline, remain in the export.

Luckily the fix is simple. All you need to do is take all iPhone footage (HEVC) into Adobe Media Encoder and export the file format to H.264 and preset to "Match Source - High Bitrate". The new .mp4 H.264 file should remove/avoid any glitches and solve your issue.

For a project that you've already built, you don't need to go through and redo the whole edit as you can replace the HEVC with the H.264 within Premiere Pro. Follow the steps below to do that:

In the project media panel:

Double click on the HEVC footage so it opens in the source preview panel.

Right click, and select replace footage.

Find the new H.264 .mp4 version of the video and press open.

The source HEVC file has now been replaced with the H.246 file.

In the timeline:

Select the clip(s) of the file that you have used in the edit and highlight them.

Right click, and select Render and Replace.

Don't change any of the settings and press OK.

Leave this for however long it takes (the longer the clips or the more effect editing you have done, the longer this will take).

This should relieve the issue. It worked for me on the one project I tried it on, so hopefully it's a permanent fix.

Another thing the Adobe team suggested I do is change the project settings so that Premiere does the encoding as soon as you load in HEVC files. To do that:

Go File > Project Settings > Ingest Settings

Click the tick box to activate Ingest

On the drop down, select Transcode.

Change the preset to Match Source - H.264 High Bitrate.

Then click OK.

From my experience of starting new projects, this doesn't look like a new setting so make sure you change it every time you start a new project. If that doesn't work, just go back through the steps above to encode the footage before you import it into the project. A bit long winded, but saves time doing it at the start rather than having to go back through at the end and render and replace all the footage post edit.

Hope this helps!