It was caused by a bug in Safari, which caused it to fail when the XR names contained spaces.
An alternative workaround for an existing rendering like the example here is to percent-escape the “folderName” value in the .html-file. This basically means to replace all space characters with “%20”.
E.g., for the example given here, in the file “Best Hardtop Complete_XR.80.html”, replace the line
var folderName = "Best Hardtop Complete_XR.80";
var folderName = "Best%20Hardtop%20Complete_XR.80";