I have opened a case with Meraki, last Thursday 9/21......and I haven't gotten a response other than the default introductory response about what version of firware and if it happens on any browser.
I am not sure I am buying the firmware thing. I am running version 12.24, which has a release date of 12/22/2016. This issue just started happening last week. I used to get blocked pages all the time. It's been 9 months since I have done a firmware upgrade??