Further experiments with this issue brings me to the conclusion that datagrid cannot handle incompatible json data!
Here is a demo, that results in a javascript error (in console) when you click on the button "get more data from server":
http://jsfiddle.net/8g89fntz/3/If the received json is not as expected, this should be handled and informed ...
I see no way to handle this because there isn't anything between onBeforeLoad and onLoadSuccess. And onLoadError doesn't get fired in this case!
Thanks in advance for having a look.