Starting Point: when we began to do Transparency processing, a workflow was introduced to assign and work on Transparencies like Papers. The switch for "always available" on Transparencies had to be set to "NO" to disallow upload of new transparencies by the authors after it had been processed.
Problem: now (I'm sure, and so are some other people that it worked before) this setting disables the transparency selection for the "Presentation manager" when the Paper (!) has been assigned (or worked on) by an editor. Somehow the separation between Paper and Transparency processing and the two switch "always available" is gone and now it's connected.