It took me a while of poking around, but it seems that when I click on the text box with the text tool and edit it, it duplicates the text layer and nests it within Landmass 1 (as opposed to the root, since it's over the ocean). The modified text layer then shoots down below the cartouche image, and the text box appears to "revert" back to it's previously unedited state. The weirdest thing is that the newly duplicated (and edited) text layer isn't selectable via the map editor, I have to find and click on it in the layer tree.
To the right is OWM, with the text field newly edited. I immediately exported the image, which is displayed on the left. The typo "DOCK WARD" has reappeared. When I go back to OWM, and try to click on the text box again with the text tool, it immediately reverts back to DOCK WARD. If I then edit the box, it disappears from sight (but is still clickable and is in the layer tree).
In this image, I've moved the text field down from on top of the cartouche, and also moved the cartouche up, revealing the duplicated text box exactly where it was before I edited it. But now it's stuck somewhere on Landmass 1's tree, and is not clickable within the map editor window. If I manage to find it in the layers tree, I can delete it.
