Look at this screen shot. I expanded then dashboard hierarchy:
There are two text boxes for "What was Cimza...", and they are both set to a height of 1. I don't know if you intend to have them there. But even more weird, if I delete them from the dashboard, they get replaced by a BLANK that occupies the exact same space, and I can NOT delete them. However, at least, with them deleted and those blanks in there, the testing I did will let you go back and forth now in presentation mode.
I would guess that something is corrupt in there, and maybe a support ticket is in order.
BTW, same deal with that empty Horizontal container in the middle of all that.
And if I create a duplicate of the dashboard, all the same behavior is in there. (I thought maybe the re-creation of the dashboard via DUPLICATE would jiggle the handle and fix things up. But no.)
Something else I did. It's not an explanation but it's a workaround.
To the demonstration mode exercise. Return to D-1 with the text box gone. Expand the hierarchy and click on "What is X's...". It will get highlighted and you can pull it down. Re-position stuff. (You'll see that some of the containers and objects got resized.) Once you do that, you can go back and forth in presentation Mode after that. The extra objects are still there, and you can't get the blanks to go away of you try to delete them, but at least Tableau has reestablished its footing on that dashboard.
Still don't know what's hosed in there. Personally, I would recreate the dashboard and move on. But Support guys could probably poke around and see what's happening in there, and if I were the DEV team I would want to know so I could patch things to prevent whatever caused this.
Thanks for the insight Joe. So the titles are still there, they are just getting set to a height of 1 when this occurs. That 2nd Cimz title shouldn't be there as it must've been re-added and saved thinking the original was deleted and gone, but it's still there!
I think the next step is to go through support.