Azure Website slow to serve static JS/CSS but not binary

Question

I have an Azure Website/Web App that is incredibly slow to serve static JS and CSS files but seems perfectly fine serving binary.

To test the problem I uploaded two

Answer 1

Looks like it was an issue on IIS 8.5 and not only Azure specific.

Now App service upgrade to Windows Server 2016 looks complete and this workaround should not be needed.