In full-screen mode, Chrome only sometimes reveals tabs -- why?

Make sure "Always Show Toolbar in Full Screen" is enabled under "View" when Chrome is open.

No, it's not just you, no, you're not doing anything wrong, and yes, it seems to be just a bug.

I had exactly the same problem. When this happens, using Command-L or any tab-related shortcut (opening, closing, switching, etc.) will reveal all open tabs, but sometimes they disappear immediately, and sometimes they don't.

From what I can tell, both the bar refusing to reveal and the bar refusing to stay visible once it does while in Presentation Mode are completely random. However, this issue appears to have been fixed in recent updates, because I haven't noticed it happening to me in a long time.

If it's still an issue, the topic Frustrating Show/Hide Tab Bar Behavior in Presentation Mode on Google Product Forums may be of use.

If I notice it happening to me again I'm going to try the solution linked. I'll update on whatever the result is.

I had similar problem but not exactly as yours.. In my case, sometimes in full screen mode of chrome and safari, the address bar and tabs bar was autohide enabled and sometimes it was not. After searching google I found the keyboard shortcut (command + shift + F) for switching applications to full screen mode, when I switch chrome to fullscreen from normal mode using this shortcut the tabs bar and address bar hides automatically.