Small delay after export

I noted your sequence settings (in the Export dialog Summary section) show a sequence frame-rate of 29.999, which is never a "normal" frame-rate. That would indicate this sequence is still using metadata from a VFR "point of view".

So I would start with a new sequence, drag/drop the 30fps clip onto the sequence from the bin, and see what your sequence setting frame-rate is. If that shows then as 30fps, you should be able to continue.

Neil

In Handbrake you need to both check the CFR crcle and set a specific number in the frame-rate box. Or it isn't fully CFR output.

Neil

Delete the Media Cache and Media Cache files:
https://community.adobe.com/t5/premiere-pro/faq-how-to-clear-your-media-cache-in-30-seconds-in-premiere-pro-2020/m-p/11017257/thread-id/260446?page=1

If that doesn't work,try resetting the preferences:
https://community.adobe.com/t5/premiere-pro/faq-how-to-reset-trash-preferences-in-premiere-pro/td-p/8236158?page=1

If that doesn't work, try resetting the Workspaces:
Reset a workspace
Reset the current workspace to return to its original, saved layout of panels.
1. Do one of the following:
• Click the Workspace menu icon and select Reset to Saved Layout.
• Choose Window > Workspace > Reset to Saved Layout.
from here:
https://helpx.adobe.com/premiere-pro/using/workspaces.html

If that doesn't work, try Preferences > Audio Hardware and set Input to None.

If that doesn’t work, try updating or rolling back your graphics driver directly from the video card manufacturer’s site. If NVIDIA, do a clean install of the latest Studio Driver (NOT the Game Driver).

If that doesn't work, try creating a new project and import the old one into it.

The core issue with iPhone footage does seem to be variable frame rates, which can best be fixed using Handbrake. Are you sure you have created a fixed frame rate version of the clip before editing this in PPro?