A method performed by a first network node, for transmitting a RLC UM, PDU, to a second network node is provided. The first network node and second network node operate in a wireless communications network. When detected that the RLC UM PDU has failed to be transmitted over a first channel, the first network node decides to redirect the RLC UM PDU to be transmitted over a second channel. The first network node divides the RLC UM PDU into two or more re-segmented RLC UM PDUs. The first network node then transmits the re-segmented RLC UM PDUs to the second network node over the second channel. Each re-segmented RLC UM PDU comprises the following indications: (a) that the re-segmented RLC UM PDU is re-segmented, (b) an order indicator related to the re-segmented RLC UM PDU, and (c) whether or not the re-segmented RLC UM PDU is a last re-segmented RLC UM PDU out of the two or more re-segmented RLC UM PDUs.