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This is an expected behaviour. With tools like jmeter and other performance monitoring tools, it is possible for BA to get choked when a sizable load is given as BA runs on the client side.
In any real time scenario, the load would come from different machines and the BA would process data at all the different machines.
When we use Jmeter, all of the requests and page loads are handled by a single client instance and the browser metrics are calculated at a very high frequency which could cause a few sessions to get missed.