We have identified a plugin conflict with ShortPixel's Enable Media Replace. We have had to frequently de-activate WP Media Library Folder in order to use the EMR plugin, but this is hassle. Short Pixel have investigated the conflict and suggested this update for WPMLF;
In /wp-content/plugins/wp-media-folder/assets/js/script.js?ver=3.0.4 on around line 1542, the script is expecting a wp.media.view.SelectModeToggleButton object present. This is not there, because it's our screen, so they should either not load that script, or have a check / regression for it.
Please contact martin[at]thewebkitchen.co.uk for more context about this error if required.