Bulk update not executing properly

Hi, I’ve run into an issue with the Bulk Update option. Once the bulk update has been activated, the progress bar just hangs on ‘Loading’. No audio files are created in the S3 bucket. I can see that when the update is run a 500 error is generated in the console: https://www.dropbox.com/s/b3rm5v2sdccufai/Screenshot%202018-02-12%2015.09.55.jpg?dl=0

Any idea on what might be the issue? I see in another thread that potentially the ‘&’ prevents the process from running. We don’t have any ‘&’ but we do have ‘#’ in post titles.

Running PHP 7.2