IDP IELTS — my result

I have given ielts twice through academic once from india and once from australia and i have been living in australia for 3 years now and both time my score was overall 7 and 7 or 7.5 each but this time when i gave my ielts exam in general category from bhatinda i got overall 7.5 with 8 in listening 8 in speaking 7.5 in reading but 6.5 in writting. I dont understand how the paper was checked how can a person be fluent and speaking listening and reading but bad at writting? There is no logical reasoning for that and when i sent my paper for re - evaluation it came back with the same result. My whole future has come to a stand still because someone did not do the checking properly speaclly when the detailed result shows that only the conclusion was a little unclear everything else was fluent including vocabulary and spelling.