To reproduce the behavior this post questions, do the following:
- 1. Create a new file container tab
2. Copy a folder tree to it (meaning: a folder with subfolders)
3. In the context menu of the tab, enable Properties->Lock - Navigation to subfolders only
4. Navigate into the folder, displaying its subfolders (and other contents)
5. Use the "Goes up one level" toolbar button to navigate "up" to the parent folder
6. Notice that the file container tab now shows the actual parent folder for the folder contained in the container (i.e., not the root of the container)
A file container tab should never allow navigation "above" or "out of" the container itself while staying in the same tab. Another way of saying this is that the "root" of a file container tab (to which all "root" navigation actions would point) should be the top level of the container, not some other location in the file system.
To support this behavior, IMO the options for navigation shown in the properties dialog for a container tab should differ from those for a folder tab. Perhaps disabling the folder tab navigation options (for file container tabs only) would be a first step.