jqgrid 3.4.3
editGridRow:complete

grid.formedit.js line ~line 646 as well as all other similar instances of this
setTimeout(function(){p.afterComplete(data,postdata);},500);

jqgrid passes a ref of the XMLHTTPRequest object (data) which is not (or may not always be) in scope at the point of use in afterComplete definition (due to setTimeout), rather it should pass a copy of the object instead of a ref.

In my instance this caused the responseText value of the XMLHTTPRequest object to be empty instead of containing the proper value.