What XBee product are you working with?
I am working with XBee ProS2B (Product family XBP24BZ7)
What firmware version is installed?
The firmware installed is 20A7.
Rate 115200 bit / second.
Have you enabled and connected the hardware flow control lines such as RTS and CTS?
We worked without RTS and CTS.
We have also worked with RTS and CTS. In this case it improves, but half of the information is lost when working by sending 64 bytes 50 times per second.
XBee works fine when we send the 64 bytes 5 times per second but not 50 times per second.
All programs have been tested with Bluetooth, which accepts those 64 bytes or more at 50 times per second.