Minecraft wiki entry for Development_versions, associated text: MC-46094 – Using fill/clone which replaces mobspawner and keeps its fire particle
MC-81202 – Fishing line disappears when fishing hook is not in view.
MC-87942 – Ender crystal beam does not appear when the ender dragon is out of view.
MC-91858 – Ender crystal beams don't show when ender crystal is out of view.