Is there any way to ensure it doesn't happen?
or give less chance of the markers being able to do that???
I find it so frustrating especially since its already an area i struggle with it makes it just that much worse that marking guidelines are so broad and open to interpretation really. :/
I think that getting feedback from as many people as you can is important to ensuring this kind of thing doesn't happen. Creativity is subjective, but just because it's not someone's "cup of tea" it doesn't mean that you'll be marked down. As English teachers, the markers are open to a range of different texts and can appreciate the way they've been formed, even if it's not their preferred genre or story style. But by getting feedback from multiple people, means that you'll be able to find common threads of "this character isn't relatable" or "this scene let me down because of the verbose imagery" or so on. Ultimately, it's your creative story so you have creative control and are in charge of the decisions, but I don't think it's right to dismiss one person's feedback, just because what that person thinks might also be what another person thinks, so at least considering it is important.
So, to answer your question, I think asking for feedback from multiple people is important. Even asking, "Was there a part where you lost interest?" Or, "Do you understand why this happened?" means that you can notice trends in people's responses and recognise where the faults in your story sit! The subjective difference really isn't great, I can hardly imagine it being more than 2, possibly 3 marks, between markers. In saying this, exceptional grammar, control of syntax, tightly controlled language, and good concepts, are always accepted by the markers. So if you nail those home, you've got some surefire marks!