csf
Hi. What browser and OS are you using?
We are running some bleeding edge software, and one of the thing I've been eyeing is bugs related to http/2. It has greater than 70% compatibility rate currently, so there are still browsers/os combinations that will not work properly. When this happens, it should revert back to http/1.1, but I still am thinking this is the cause of the issue and may be more a nginx + http/2 bug.
Are you using safari by chance?