For the multi self.connect problems

Hello,
I recently have a problem to transmit the MIMO signal and I need some
helps you guys.
What I am trying to do was to send the preamble from each transmitter
daughter board first and send the actual data. The problem is that when
I try to use as below. It did not work:

… … …

    self._setup_usrp_sink()

    self.connect(intl,self.u)


def _setup_usrp_sink(self):

… … …
self.connect(self.preamble1,
self.chunks2symbols13,self.rrc_filter3,(intl,0))
-----------------------------(1) self.connect(self.preamble2,
self.chunks2symbols14,self.rrc_filter4,(intl,1))
-----------------------------(2)
self.connect(self.ala1, self.chunks2symbols11,self.rrc_filter1,(intl,0))
-----------------------------(3) self.connect(self.ala2,
self.chunks2symbols12,self.rrc_filter2,(intl,1))
-----------------------------(4)

I know that I am not supposed to use the multi-self.connect. However,
self.preamble1,2 and self.ala1,2 are the finite data and as soon as the
(1) and (2) was done, the (3) and (4) are supposed to work.
Unfortunately, it was not. Could you give me what the problem is and
also, could you give me any advice how to transmit the different datas
with different constellation with using self.connect?

Thanks,

Joon Kim