At the bottom of it all, be aware of how the platform stores the app data. This advice helped me to debug a perplexing issue.
A change in Google Fonts' URI structure for embedding combined fonts can lead to an incompatibility with WordPress.
When you muck around with PHP enough, every now and then you'll find a skeleton in the closet.
Enable WordPress AJAX requests to set the language locale through WPML with this small patch.
An interesting gotcha that I stumbled across recently, sending a 404 response code with a download forced by Content-Disposition: attachment will fail but inline content will still be displayed. This behaviour was tested in both Chrome and FireFox. Of course the appropriate response code should always be sent; this 404 response code was being sneaked in by WordPress and led to hours of frustration.
A rather frustrating bug that I became aware of when generating navigational menus for custom post types using wp_list_pages(). The list entries aren’t decorated with useful classes denoting the current item, the parent item, and ancestor(s). Read about the issue here.