I just tried to change the driver to S7 400, but, as expected, the behavior is the same as the S7 300: the error is logged, but the communication works correctly.
Sorry, but I cannot replicate your problem. Other than the error logging, the communication and the variables work correctly, I have no issues at all. Which version of Ignition are you using and which operative system? Maybe the behavior changed in the newer versions or with a different OS (I’m using windows).