I need more information though.
Did it happen just once ?
Do you know what thread it was ? (This could be relevant if there is a post embedded content from a site requiring it's own scripts. Facecook,twitter, etc)
What's the platform you're using ?
Browser on your end might simply have not properly loaded the header data in your browser for some reason. If it's just the once, I'd probably guess it was either just a Chrome mini-screw up or maybe our cloudflare skipping a beat.