We were not able to find out how to debug the issue - Chrome Dev Tools profiler does not show where the delay comes from. We will log the issue as a bug and will re-investigate it as soon as we find a way/tool to debug it. I am afraid that I cannot commit an exact time frame when that will happen.
Please accept my apology for the inconvenience caused.
Meanwhile I can suggest not using the private browsing mode, or if it is required for your users please disable the pushState option of the application.
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