Switching between projects

Does anyone know what the method is behind how FCPX chooses which projects are available to switch to using the back and forward arrows at the top of the project sequence (to the left and right of the project name and TRT)? This has made me crazy for years. I'll open another library to find a project to pull some footage from, and the project I was just working on is not selectable with those arrows. I have to go back to the browser, find it, and reopen it. The only projects available to switch to are random ones that I haven't even opened.

You mean above the "Timeline" pane? Yes, they are in the order you've opened them. I've never noticed random behavior like you're seeing. Try trashing preferences (Opt-Cmd-launch).