Product and version - FMPA 184.108.40.206 64-bit
OS and version - Windows 10.0 Pro (Build 14393) 64-bit
Hardware - Dell Precision T3400, Intel Core 2 Duo 3 GHz, 10 GB RAM
Description - When a container field is set to Optimize for "Interactive Content" and positioned in the upper left corner of a layout that is opened as a Card, the close button is not visible. Clicking where the button is supposed to be will still close the window, though. Changing the container field to Optimize for "Images" does not have this problem, but then you lose the desired functionality. This is also not an issue on a Mac.
How to replicate - Create layout with container field so it is in the complete upper left. Set field to optimize for Images. On another layout, script New Window step to open container layout as a card. The close button will be visible. Then change container field to optimize for Interactive Content. Run script again to open New Window, and the close button is hidden, but it's still functional.
Workaround - The only, true workaround that maintains the field settings is to position the field low enough on the layout so it does not overlap with where the close button would appear, but this leaves an unwanted space at the top and is not a permanent solution.