You hit the max number of segments that Google Earth can display in
one path. Note that when you open the properties window, only red
squares appear where the vertices of the line are, not the line
itself. But the limit is somewhere between 30000 and 35000, I suspect
2^15 or slightly less, and your path only has 6973 segments. It failed
because the tessellate option told Google Earth to add extra segments.
Your path isn't sensitive at all to the problems that could occur
without the option, so it's safe to disable it. To disable it, extract
the KMZ file as a zip file (rename to .zip or force the zip utility if
you can), which should give you a file doc.kml. In that file, look for
<tessellate>1</tessellate> on one of the last lines, just before the
really long <coordinates>6974 vertices</coordinates> line, and replace
the 1 with a 0. Then save the file and open it the file in Google
Earth to see if it works. If you want a small KMZ file again, just zip
KML file and rename to .kmz. I'll upload my result as "recorrido
fixed.kmz".
Jonathan