Hi, this sounds like you are runing two different load tests.
1) 10 vu, the result is everything goes well
2) 500 vu, the result is all or parts of the system under test resports errors, stops responding as expected, and so on
May I ask about what methodology you are using, how it looks? What is your method to identify load levels your system can cope with, how to do go forward to see WHEN things go bad and at that point to identify WHAT went bad?