Howard Miller

Google Lens claims... "Mixed active content blocked". Which is interesting...

 

That implies some mix of http and https is going on. I'm not sure how that would happen with file upload. Server misconfiguration?

 

To the OP - I can see that the URL of the fileupload javascript is http? What is wwwroot of your Moodle site? Is that also http or https? Http would be very unusual for a live site these days.

*something* is causing the filepicker javascript to fail.

Is there any other javascript included on the page or, more likely, some unsupported or obscure plugin?

I opened your file in jmeter and, at a glance, it looks perfectly reasonable to me. Have you considered increasing the ramp up period? I'm far from an expert with jmeter but what happens if the site doesn't have the capacity to ramp up 2000 users in the requested period of time?

I can't begin to answer the second part of your question. You've got some "unconventional" stuff going on. I assume that Moodle appears to be working properly on this platform?

I really don't think it's Moodle doing that.

Check your web server logs first.

It was very specific to us and not something somebody else could easily use.