How can I write the End point Firmware on XBee Pro S2B?

I’m having problems to write the End Device AT v28A7 to a XBee Pro S2B using a FTDI usb.
Every time I wrote the firmware, the XCTUNG stopped recognizing the board and keeps asking me to reboot the device.
The Coordinator AT and the Router AT works well, but they can’t communicate very well with each other, the messages are hiccuping even with a 100ms delay between messages.

Thanks in advance,

For the Communications between a Router and a Coordinator, try setting the DL and DH of the Coordinator to match the SL and SH of the router.

The reason you are having to reset the End device is to wake the end device up so you can talk to its UART. You see end devices sleep most of the time and you need to either try talking to it while it is awake or reset the module to wake it up.