On the rebuilt surface that @pascal had you create, with the large number of UV’s, you need to switch the surface directions so that U’s become V’s and V’s become U’s. To do this, use the Direction command (type Dir). Choose the Swap UV option. After this is done, try the Flow Along Surface command (not Flow), and I think you will find that it now works. The problem was that your original base surface’s UV’s were opposite your target surface’s UV’s. When you ran the Dir/Swap UVs command, both base surface and target surface U’s and V’s now run in the same corresponding directions, and the results of the Flow look correct. Actually, you could get the correct Flow results if you used the Dir command on either the base or target surface. The net result would be that after running Dir on either, the U’s and V’s would match and Flow Along Surface would work as expected.