Although FIFO is choosen for the itemgroup are certain items not always picked in the right order, all setting seem to be right. Is this a known error??? Is there a known fix for the problem?

FIFO is financial, this does not mean the physical stock is suggested to be picked in this order. For example book in batch 02 on 30.05.13 at $5 and then batch 01 on 31.05.13 at $7, financially it takes the average and then the $5 but physically would suggest 01 as it is less, and then if you financially cost by batch it would swap the $5 with the $7. In AX2012 you use FEFO picking with expiry date control.