@nl-setech we haven't been able to find something on our side, so it may be an issue specific to your app. A guess: it seems likely related to screens being renamed or deleted. I would check your tab bar configuration to make sure that it's not referencing any nonexistent screens. The state debugger may help with inspecting the specific values.
So, after freaking out, and reverting a bunch of times. Reverting didn't work at all. I reloaded the page, and it came back. Kind-of not a great end-user experience, but worked out in the end. So, good now.
Sorry to hear the reverts didn’t work, but glad reloading helped in the end. In general, hard refreshes and / or closing and reopening the app tend to be a good debugging step. We know it’s not ideal, and we’re always working to improve things. Let us know if you run into any other issues!