Hello Daniel, I will continue through the forum with this issue (the email address you gave me is the same as the one that gets returned, so I won't take the chance for not reaching you).
I have noticed jQuery and jQuery UI are still loaded (in a strange way that can not be intercepted by jQuery Easy) by jReviews. I have disabled it from the component in the administration console and put it back, realizing that you actually are not using jQuery Easy on all pages where jreview is present, which can be a problem.
I have also noticed Google translate scripts are added twice on the pages (mod_gtranslate). That could be a problem also.
The ""cannot read property 'createDocumentFragment' of null error"" is usually because a script references an object that does not have an ownerDocument. Therefore one of the scripts on the page has an error, but I was not able to locate it so far. It actually may be because of the tooltips: there is a conflict because Joomla calls the Tooltips from Bootstrap and some other script calls tooltip from jQuery directly. These 2 are not compatible. I don't know what component adds the tooltip code. The Bootstrap one is added by Joomla. There is no option in jQuery Easy to disable either one.
One notice: the 'createDocumentFragment' error happens when leaving the browser and going back over the page. So it may also come from a script that checks if the page has focus.
Olivier.