The taxi route given by ATC wants you to follow "nodes" set in place by the scenery developer. If you go off course, ATC will tell you the course again. With XP 10, the yellow taxi route given by ATC was relatively easy to see, and therefore easy to follow. It's much harder to see the taxi route in XP 11 (the yellow coloring is very pale). Therefore, ATC will let you know repeatedly if you are not on course. Maybe they will fix this in future versions of XP 11.