That doesn't help, he supposed to know, he needs to read his console to find/pinpoint the error. Or share a screenshot of the console error logs, if he is looking for outside help. Although, I believe he just shared that screenshot for members to understand he is trying to fix an error and he will sort it out in due time / needs some extra time to fix the issue
But I would say (guessing and assuming on the little information) that one of his plugin or commands is not set up right or missing. Seeing as it is a set, he should look at his plugin list order and change their priority depending if he added anything new. Or plugins that he forgot to setup or inputted incorrect parameters. If all else fails, he can just try disabling one by one to find the culprit if he forgot what he did. This works nearly all the time. Other little things can throw the exception but most likely it is plugin issue. Just my 2 cents on the little information.
Some suggestions would be,
backup is the key. Especially for a dev. He can easily copy an old plugin js folder and test or only the main global files in the data folder. As any added asset wouldn't matter at launch. The game should launch fine after.
Thanks for sharing btw