Hi Umair, I agree with Ola.
As I see it, you ramp up up your load in big chunks. For the first few chunks (maybe onl one) everything is good. Later, as you increase load, you start to see how the system you test is starting to report errors.
This is expected to happen if you manage to inscrease the load high enough.
When it happens, and also before, you have to make sure you know what the logs (and possibly counters and metrics) say.
If these are your first load tests for this system, you might be surprised at the low level of the capacity the system has - so maybe you have something badly configured, something which is more developer friendly and less production like?