I believe that I have the same or similar issue and my MODBUS serial connection stops work almost immediately. So I can’t now control lights and sockets or read any registers from my PLC 
How can I separate MODBUS logs to have full TRACE log?
I have found description for SONY binding https://community.openhab.org/t/sony-devices-binding/14052, but don’t know how to set it up for MODBUS.
