I'm considerably confused about what's happening with Mailer & images (initially, I thought the problem was related to Mosaico, but it's now disabled): weirdly, I can upload an image to a newsletter draft -- and see it there, in the draft . . . but I cannot see it with KCFinder. I can't see anything at all in KCFinder, and it spits error messages back when I try to navigate to subfolders.
The image directory is: [civicrm.files]/persist/contribute/
Indeed, uploaded images (from either Mailer or Mosaico) land happily in this directory, but I can't view or use them from within CiviCRM.
Been reading related issues for days, and I can rule out imagick (specifically related to Mosaico) & permissions (settings are normal, at 755 for directories and 644 for the images themselves). Any insight would be most appreciated!