Weird smudging problems with illustrator CC 2017

Hi everyone I'm having an issue with illustrator and its really annoying. I start doing a project then when I move things onto an image or or go across an image as I'm moving something it creates this weird smudge which appears to be sharp triangular shapes?

Here's an image of the problem. As you can see at the top of the pattern it's all smudged and when I image traced the lady it leaves a sharp shape.

I hope that makes sense and hopefully someone can help as its really annoying and I can't really do anything.

Thanks.

Josh.