Initial Lock issues


I’m using two xbee pro S2Bs…I’ve set one as the coordinator and the other as the router. I know for a fact that the network works because data does get transmitted across the link properly. However, I find that the coordinator takes some time to lock to the router and this time is rather unreliable. I’m planning to use the xbee to send an ignition signal to an amateur rocket, so I need a degree of reliability from it. The way this works is that I press a button which causes a character (say ‘F’) to be written on to the serial port which is then received by the router and upon receiving ‘F’, it tells the arduino to send the ignition signal. I’ve tried a bunch of things but can’t seem to fix the problem.

I’ve also seen something else that strikes me as strange…I try and send a test sequence out to light some LEDs to indicate lock, and I find that when I send a sequence that’s 4 bytes long - 1234, that seems to be rather unreliable…however, within the scope of my testing, when I send something that’s 9 bytes long - 123456789, I get 124689 at the receiving end, every time. Now, I can get this to work, I think, but I still don’t understand why this is happening.

Does anyone have any idea about what might be wrong?

Thanks in advance.