how Wireshark reassemble SMS in NSS interface?

Hi all

I'm working on the gsm signaling data and now I have an data that related to NSS interface (I mean this data has the hierarchy like this --> MTP2, MTP3, SCCP, TCAP , MAP and SMS)

In some of SMS data I have an SMS which has TPU-header and this section show that this SMS has another parts. In the TCAP which we have RP information and by using them and the header we can concatenating SMSs. But in the TCAP we don't have any information about RP-OA and RP-DA--I mean both of them are nosm-RP-OA and nosm-RP-DA! So how should reassembles them? I think Wireshark in this interface has some bugs! Since I have some packets that TP-OA address are not same but Wireshark reassemble them! Is there any one experienced this problem and how solve it?

thanks