Sorry for no reply to this post. I think i not saw it in December.
You can check if this also happens with the new version released today for 2.3 or if you updated in the mean time to 2.4 you can install the “readfish_extension” mkp linked here Redfish extensions for existing integration in CMK 2.4 until the code is in the normal CMK mainline.
I had some changes inside the code for Item names to prevent the problem from your post.
If i should test something with your device output, i need as a minimum a complete agent output or better an interface mockup dump described here Call for Redfish beta testers