LoadEvent and DomLoading take too much time -- open edx devstack

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Hy, 

I'm facing a very annoying issue : When i load course on the platform it takes too much time. It's the same when i try to navigate to another section in the same course. There is the time diagram i've got for example attached to my message. 

Any idea about this please. How can i debug it efficiently ? 

Regards,