unwanted swap of values in field collection

I have a field collection (FC) [multi-value, not required] with
*a required field (REQ) which is of type "content reference".
*a non required Text List field (TLIST)
*a simple text field (TF)

FC is attached to a node and "REQ" is using IEF (complex).

Here are the steps to reproduce the bug:
1-Create a node with 3 FC completed
2-Save it and re-open it
3-Using Drag and Drop, change the order of the 3 FC

Expected result: nothing except the change in the order
Bug: The value of TF have not followed the drag operation.

Exemple:
Before drag
(REQn is a value of the REQ field,... same for others)
FC[1]= REQ1, TLIST1, TF1
FC[2]= REQ2, TLIST2, TF2
FC[3]= REQ3, TLIST3, TF3

After Drag
Suppose we drag FC3 at the second place.
The expected result should be:
FC[1]= REQ1, TLIST1, TF1
FC[2]= REQ3, TLIST3, TF3
FC[3]= REQ2, TLIST2, TF2

But the result is:
FC[1]= REQ1, TLIST1, TF1
FC[2]= REQ3, TLIST2, TF2
FC[3]= REQ2, TLIST3, TF3

This problem doesn't occurs if I use the auto-completion widget for the REQ field instead of the IEF.