Do you mean when you turn off "Improved app rendering" it works ok and when you turn on "Improved app rendering" , it doesn't work fine?
Are your all Apps' Galleries all as this?
Could you please try with anoterh browser to test it?
The "Improved App Rendering" functionality is used to render an app in more efficient way. The "Render in Classic mode" functionality is used to render an app in a classic app rendering way.
Some new experimental features released within the canvas app are based on the "Improved App Rendering" functionality, In other words, if you want to use the new experimental features (e.g. Try the enhanced Group control) within the Canvas app, you must turn on/enable the "Improved App Rendering" option.