I am getting a very similar problem.
When encoding and audio file in javascript I get the following error: "Uncaught could not load memory initializer Mp3LameEncoder.min.js.mem"
The HTML file with the corresponding javascript libraries are in the static folder and the HTML file is called as "TemplateView" in the Django application.
PS: The code without Django/Python has been tested on another server and worked without issues.
From what I gather the webserver has to be configured to support these ".mem" files
<system.webServer>
<staticContent>
<mimeMap fileExtension=".mem" mimeType="text/html" />
</staticContent>
</system.webServer>
Any idea how I can resolve this issue?