When you open a tab in certain Dashboard it will show you "Tab is broken"
This issue arises when the "Canvas page" is empty for that tab in pa_tabs table.
The solution would be to manually add the canvas page back for each of the tabs in the instances. To add them back in the other instances:
1. Navigate to pa_tabs.list
2. Search for the tab(where you are seeing the error)
3. Add the Canvas Page to the Personalized List Column.
4. The Canvas Page should be empty.
5. Add PA tab.