I have a multisite install with 5 sites running the newest version (4.6.1) and I've been having this problem since before upgrading to 4.6.
I have Buddypress installed on multiple sites and I'm using BP Multi Network to have a separate network on each site. On any of the sites (within the last 2 months) when I try to create a new Buddypress Group, I get the "Are you sure you want to do that?" error message. The group is still created, but I have to go back and finish the setup process to make it work.
The error message ALWAYS shows up, but not always on the same step. Sometimes it happens when choosing if the group will be public/private, other times it happens when I am should be able to enable forums. When the error is about to happen all other text except for the headline and the forward and back buttons is missing. See attachment.
What I've tried:
I disabled all plugins except for Buddypress and tried to create a new group: still got the error message.
With only Buddypress active I tried switching my theme to Twenty Sixteen: still got the error message.
The error happens across all sites in the multisite.
I'm hosting with Rackspace under this setup:
2gb Server for Database
4gb Web server
4gb Slave Web server
I'm at a loss. One of my sites is a Dev site that is a clone of my main site so I have the ability to test without breaking everything (except when I disabled all plugins, that affected every site)
http://www.theholler.org is the main site
dev.theholler.org is the dev site