Interesting discovery you have here.
If what you say is true then the printer may not be communicating over the network correctly. Something like that could only be a firmware issue which HP would need to fix.
Can you tell us more about this problem so we can better document it? For example is there a specific kind of network traffic that generates these bad UDP packets? Aside from the usual network chatter the printer should only be communicating over the network when performing a scan or print job. It would be interesting to know from there if specific file types trigger the bad packets.
Do these bad UDP packets break any of your systems or cause other issues when they are detected? Does the performance of the printer or the email server suffer from this defect? Can the end user tell there is a problem or is this purely an administrative issue in your enviornment.
If ESET is aware of these bad packets and knows there are no serious issues then perhaps it would be easier for them to filter what they report in the security logs than to get a response from HP.