Lost bytes in sending data from Arduino to Android via Bluetooth


I want to send data from Arduino to Android via Bluetooth. I use HC-05 bluetooth in Arduino and use SoftwareSerial library. The baud rate is set at 115200, 1 stop bit, 0 parity. I have tried other baud rate but so this is the best so far. I have no problem in sending data to Arduino, but from Arduino to Android, it seems that Android read lost bytes too often. Mostly the 2nd byte.

For example, if I send an MQTT message, The remaining length part is lost, and it will caused error in decoding the message.

I use this Android and Arduino library source

What caused this lost bytes? and why it happens?