Problem communicating four Xbee S1 802.15.4 modules to one Xbee S1 802.15.4 module

Hello all. We are trying to send data of 88 bytes, 36 bytes, 36 bytes & 20 bytes every 100 millisecond from 4 different Xbee S1 modules to a single Xbee S1 module. All the 5 modules are configured for peer to peer communication in transparent mode. The application demands that 4 modules may be turned on anytime and so there is no way of synchronising the transmitting modules. The data recieved by the reciever module is continuously monitored. But the receiver module does not receive all the data sent by the transmitter modules. However, if any three trasmitters are turned off and when there is only 1 transmitter, the reciever is able to receive all the data sent by the transmitter correctly. Is there anything we are missing to consider while communicating with more than one modules?

The settings made are as below:
Transmitters:
ATID 3001 // Same for all transmitters
ATMY 2 // Unique
ATDH 0 // Same for all transmitters
ATDL 1 // Same for all transmitters
ATBD 7 // Same for all transmitters - Baud rate: 115200
ATCN

Reciever:
ATID 3001
ATMY 1
ATDH 0
ATDL 2
ATBD 7
ATCN

Thank you,
Raj_tz