I'm working with a couple of dozen Drupal 8 sites, and I'm experimenting with Media Library. What I've found is that on the new sites I build with 8.6, Media Library works like a champ. On older sites that I built in 8.4 or 8.5, and have upgraded to 8.6, the media_bulk_form field in the view has a "Broken/missing handler" error.
Poking around the database, I found that these four actions didn't exist in the config for the older sites:
system.action.media_delete_action
system.action.media_publish_action
system.action.media_save_action
system.action.media_unpublish_action
Exporting them from a newer site and importing them into the older sites appears to fix the problem. Should these be installed automatically with the Media Library module?