Hi Patrick,
It seems like Agent is unable to format the metric name properly, indicating one or more of the entities enclosed in {}(hostname, queue etc.) is either unavailable or looking for same is causing an error. Instead of suppressing we should look into addressing the root cause so I will suggest you to open a support issue with following details:
-WAS version details including logs
-Agent logs in DEBUG mode
-MQ Client API version used by Appserver
-MQ Server version details
so we can help you further.
Regards,
Kulbir.