Random parts of audio dropping out after export

make sure your source audio sampling rate matches your sequence sampling rate and that all audio is uncompressed using formats like aiff or wav...  Although Premiere is pretty amazing the way it can work with almost anything you throw at it, mis matched sampling rates and audio compression can cause issues...    Generally, in the professional video world, audio is 48k uncompressed. ...  In the crazy world we live in now, not so much...

Also:

Please use the free MediaInfo and post a screenshot of the properties of your media in tree view:
https://mediaarea.net/en/MediaInfo

Many users are having issues with VFR. If the file is variable frame rate, use Handbrake to convert to constant frame rate:
https://handbrake.fr/downloads.php
Here is a tutorial:
https://www.youtube.com/watch?time_continue=34&v=xlvxgVREX-Y

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 installation 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.

Also, please help us help you:
https://community.adobe.com/t5/premiere-pro/faq-what-information-should-i-provide-when-asking-a-question-on-this-forum/td-p/3929027?page=1

I've moved this from the Using the Community forum (which is the forum for issues using the forums) to the Premiere Pro so that proper help can be offered.