A pen stroke shorter than the pen's minimum step keeps one point and is
drawn as a dot whose radius is clamped between one pixel and scale(2). On
a map area under 415 px tall scale(2) is below one pixel, so clamp threw:
the app showed "A UI error occurred", the stroke was never finished, and
the next stroke the user drew was joined onto it. The web beta reaches
that size in a short browser window. The upper bound now never drops
below the lower one.