Howard Miller

Let's start with which version of Moodle is this?

 

Are you using the standard Boost theme? If not, please try again with Boost to see if it makes any difference. 

 

Javascript errors in code that's known to work and most often caused by broken JS somewhere else. Have you any 'suspect' plugins? By that I mean, ones that are little used or not the correct version - that kind of thing. 

 

Also, are you injecting any random javascript into the header/footer for analytics or similar? It doesn't take much.

The Chrome message is nothing to do with it.

My first thought would be some customisation on her Dashboard that's linking to something that doesn't exist (any more)?

The way forward is to enable full Debugging, get her to recreate the issue, and recording the full error trace. That will help us to identify the problem.

Read / check - Using_slash_arguments

 

If your web server is nginx and you have not properly configured it for Moodle, this WILL be the problem.

Sorry - I know nothing at all about React.

 

Although - a quick Google suggests that error is an SSL problem.

...and, if you don't have a proper cache then get Redis.

You don't say so, but if you're moodledata is on NFS then that's almost definitely your problem.