For presenting & prototyping in-browser, the order of the Artboards should be changeable or controllable.
Currently, it appears like the Artboard order rearranges to when changes were last made.
In order of preference:
Honor the existing Artboard order on the Sketch page:
a. visually left to right, then by rows top to bottom
b. by Artboard stacking order in layer list by Sketch default (currently bottom to top)
Allow manually fixing the error in the browser
a. by drag n drop