Arduino ModbusRTU Demo's failing on MKR1000-MKR1010

I have connected an MKR1000 to an MKR1010 using 2 RS485 MKR shields.
Both can send data back and forth without trouble.
I tested this using the RS485Sender and RS485Receiver demo’s on both shields so I am sure they can send data back an forth.

Does anybody have a reference of this kind of Modbus Mkr configuration working properly?
(Dip switches are set as requested in the example comment, MKR’s are fed using the RS485 shield, shield is fed with 8V using a stabilized power supply, line between the 2 boards is 10 cm, gnd’s are connected, signal levels seem clear on my oscilloscope.)

ModbusTCP runs without troubles (using MKR ethernet on the same configuration of course).

Best Regards,

As Modbus RTU uses the RS-485 physical layer, it will work using exactly that setup you already have.
Maybe I misinterpreted your question as I don't understand what exactly your problem is.