Hi Ulrich,
Unfortunately, we don't have more information regarding this error, just what's mentioned on the RM: This bit is will be set to '1b' when an Error response is seen to a read on the system interface.
Have you tried debugging this issue? What is your software doing when this error happens? Are you using our evaluation board along with the examples that we provide within the SDK? If so, please tell me how can I reproduce this on my end to see what might be the root cause of this behavior.
Regards,
Victor