Hi,

It is related to a security fix done in 4.11.0: https://downloads.prosysopc.com/opcua/Prosys_OPC_UA_SDK_for_Java_4_Release_Notes.html#version-4-11-0, relevant part copied below:

“… security fix limits extra info in OPC UA TCP ErrorMessage and in the ResponseHeader(s) returned with any ServiceResponse. Now by default they do not anymore contain any additional info nor stacktraces of any Exceptions that would occured within the processing of the ServiceRequest. We are not aware of any attack scenarios where this information could be used, but it could potentially be useful for an attacker. The fix disables the functionality of ErrorMessage.setReason(String) and DiagnosticInfo.setAdditionalInfo(String) unless flags ErrorMessage.disableReasonField and/or DiagnosticInfo.disableAdditionalInfo are set to false (default true). The disableAdditionalInfo also omits the StringTable of the ResponseHeader when built from an Exception. Future SDK versions might offer more granular control.
“

Note that without the above SDK will use the AdditionalInfo already by itself in most cases for the stacktrace. The one you are trying to use might be one of the few that could allow putting custom text there. But we do not yet offer any “more granular control” for this.