I've been getting this error popup every single time I go to customization scripts/deployments -- /javascript/NLUtil.js' not found

Probably requires a support case

I found out the error pop-up only occurs on Chrome. I switched to Safari, and the error disappeared. I have not tested Firefox. I am on MacOS.

And it doesn’t happen in all NS environments…

Did you try in incognito mode ?

I haven’t tried that and it’s probably worth a shot

I think it's related to a plugin - I suspect

NetSuite : HTML Script Notes

Check your browser console for errors

Yeah it's probably an extension that's why suggested incognito.

Incognito works and it’s quite plausible that it has to do with that plugin.