I don't know where that "preloader.png" file is coming from.
Normally, when you export as "HTML5 website" all the images of your project are exported within the folder you indicated, except "loading-logo.png" and "icon-x.png" which are expected to be at the root with the JS file, since they are "favicons" and "utilities" images.
I don't know about a "preloader.png". And there's definitely no trace of such a texture in the capx you posted on top of this topic.
But as you've seen yourself, the 404 error, the "bad serving of resources" is causing part of the issue, and you can fix it by either making sure of your server or modifying the exported js file or just putting the files at root, where they are expected to be.