Cursor moving to next record when refreshing form

Hello Dax community, 

I am facing issue i never seen before, when i refresh my form the cursor move to the next record as if i was doing MyTable_DS.next(), to check this issue i have overriden task method on form and the cursor is moving after the super(Task_id) 

it's a very strange behavior, code for method task below:

public int task(int _taskId)
{
int ret;
PurchAgreementHeader test;
test = PurchAgreementHeader_ds.cursor() as PurchAgreementHeader;(there i have the currentRecord recId)
ret = super(_taskId);
test = PurchAgreementHeader_ds.cursor() as PurchAgreementHeader;(there i have the wrong record: next record)
return ret;
}

Thanks in advance for your help.

Mehdi SOUIHLI