Not sure if this applies to any of your setups but I had a similar problem with 'Oops! Try to close the page & re-open it properly' using PHP7. I found that I didn't have all the necessary packages installed on my VPS server. With all the packages listed below installed the error disappeared and so far it is working ok.
I am using WHM on VPS CENTOS 6.7 with EasyApache 4 which allows me to select different php versions for each site.