Another option to proceed is the use of a Modbus Master Simulator.
I have been using the Radzio! Modbus Master Simulator.
[Modbus Master Simulator]
Note:
I am NOT suggesting that your problems are caused by OPENHAB.
I have been using the Radzio! Modbus Master Simulator to investigate the “lost byte problem”.
It helped me to find out that the “lost byte problem” was caused by SMA.
Feel free to contact me for further investigation !