Data is not saved across log out / log in + Negative Steps

In the DataViz, we can have a negative step count....? This happened when logging out and logging back in via the QR code. Hence, going back to the previous study, which already ran on the phone previously.

It seems like data cached locally on the phone does not survive a log-out / log-in cycle. This also applies to other kinds of data, like the number of tasks done, which is reset to zero.

But why negative steps, and not just resetting to zero?