The mootools.js file contained a byte order mark at the beginning of the file that resulted in an occasional "unexpected end of input" error message when loading the library in Chrome (version 61.0.3163.79).  Using a "hard refresh" (Ctrl-F5) 1-3 times would generally cause Chrome to load the javascript correctly, so the error was intermittant.

This error does not occur on Microsoft's Edge browser.