Well, with all testing remember you need a way back. Don't do it if you are unsure how to get back to where your settings worked for everyone/all devices.
My testing worked for me and the 610 has been great since.
Start by powering off your router and all devices; power it up; log in; save your settings; clear the router log files; then try connect with the 610
There may be something meaningful to use then
I do think it is an issue in the 7.5 code