Error output to Builder interface

I've been experiencing a glitch with Metabox Builder on the "Edit Field Group" page, where an error is output to the screen which says the following 3 times: "[an error occurred while processing the directive]"

It doesn't seem to be affecting functionality, as I can still create field groups, but it is annoying, and doesn't stir up confidence... I wanted to use Metabox on a project we started recently, but this issue was enough to turn off the other developers to using it (too late for this one, maybe next time though).

There are some JS warnings in the console which may or may not be related:
https://pixablaze-397923.d.pr/OqTrb5/JRkfv4DkGV

I can't seem to reproduce the issue on our production sites, so I can't really share a login or anything as it's only happening on our local environments.

We're using Laravel Valet on Macs, so guessing the environment may be related. It's Nginx, so that makes me wonder if it's related due to the "directive" language in the error.

Apart from the server environment, everything else is default and latest versions. I've even tested on a brand new install, multiple times, same issue.

• Latest versions of Metabox + MB AIO
• Default TwentyNineteen theme, no customizations
• No other plugins even installed
• Latest WP
• PHP 7.2, Mysql 5.7, nginx/1.15.8

It's not critical for us at the moment so no rush, and I'm not sure how else I could help troubleshoot but if you need any other info let me know.