Bug - For rearranging columns in flat mode

Open this fiddle:
https://jsfiddle.net/sohansoni/afr1g5Lf/6/
Try to rearrange columns direclty on the screen i.e. by selecting one column by mouse , drag and drop and change its sequence. Column position will change.
Now open fields widget, and say Ok. Columns will be rearranged with the sequence from fields widget.
Now rearranging columns from the screen by mouse does not work. You need to go to fields widget and rearrange from there.
Let me know if you need more information.