What openHAB sent over serial, a Modbus query
The response openHAB got, where an error was detected.
Of note - first byte FF, second byte 01. third byte 03
What we would expect to see in a response is a mirror of the first few bytes of the query … in this case 01 03
So it’s clear that noise or a glitch on the line has started the process of receiving bytes prematurely, inserting rubbish data in front of the real stuff.
FF is what you get from a glitch starting the UART, followed by normal idle line.
In short, yes the error here originates at your serial bus. If it seems periodic, it is most likely electrical noise picked upon the RS485 line. This wouldn’t be surprising near an inverter - lots of high current switching to generate noise.
Just written a spiel, won’t copy paste, latter part of this -