M340 BMX P34 2020 modbus TCP with Phoenix-contact Bus coupler


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From M340 embedded ETH port we have a direct link (EHT cable, RJ45 connectors ended) to à bus coupler from phoenix-contact reference 2703981 (IL ETH BK DI8 DO4 2TX-PAC).

All basic settings are OK (IP addressing).

With Unity Pro configuration software:
-bus coupler data reading is OK.
-bus coupler reset (writing value 6 to 2006 address) is OK.
-bus coupler Digital Output control (Write data) is not good.

Phoenix-Contact technical support was in our office yesterday afternoon, checking programming code (unity) and bus coupler configuration. They could not solve the problem and they concluded by this sentence:

M340 Modbus request is not good using embedded ETH on P34 2020 CPU. This problem is said to be well known and Schneider is asking people to use the CANCEL EF.

Their proposed solution is to use IO Scanning card from Schneider BMX NOE which is working perfectly with phoenix-contact bus couplers.

I do not appreciate their solution as they are accusing Schneider, and solving the problem with an other hardware.

Is there someone who experienced such a problem?