I have an XPages app running on 8.5.3 UP1 with a mobile controls interface. It works fine on my dev and test servers, but in production we\'re seeing the following intermittent
OK this turned out to be a very odd issue which affected iOS devices specifically. I had written some extra code to detect if the app was running in standalone mode (ie that the user had created a shortcut to the app on the home screen). This code loops through all tags that have an onclick event and stops them from launching Safari and forces them to run inside the standalone browser window. In the case of the load more button this is what was causing the error on the server. I still don't understand why that was an error, but it was an easy fix, simply don't process the Load More button when I loop through everything else in the page.
Thanks for all the help everyone.