I have a rich:dataTable containing input components (in our case, comboboxes) in each row, and an attached rich:dataScroller. Since we want to submit changes made to the comboboxes, the dataScroller's ajaxSingle is false.
This works fine - until the users click the the dataScroller faster than the server can answer the AJAX request. Then, the second request fails with a validation error. Here's a slightly sanitized output of a4j:log: