When working on captions, deselecting the captions clip in the Timeline (or selecting any other clip) makes all of the captions disappear from the Captions window. An empty Captions window is of zero benefit to editors and is an annoyance since it gives editors the added step of having to re-select the captions clip in the Timeline before they can continue to work on captioning.

My suggested solution is simple. Please always keep captions visible in the Captions window, whether the captions clip is currently selected in the Timeline or not. If the Timeline has 2 or more captions clips, keep the last selected captions clip visible until the editor manually selects another one, or one gets selected automatically through "Selection Follows Playhead".

For 11 more Caption issues (5 of which have already been fixed), take a look at this thread: https://adobe-video.uservoice.com/forums/911233-premiere-pro/suggestions/38080990-everything-wrong-with-captions-in-premiere-pro-13