The 91% complete issue is a problem with Precision Farming, not the map (I assume you have PF installed?). If you update PF, you 'should' be able to complete the field, but the 91% bug is still present.
If you check, wheat also has two planting times - this reflects real life as 'summer planting' is a thing for those crops. In real life you get less yield, but I am not sure how that is reflected in this map.