Welcome to the Q&A Forum

Thanks Cyrus, thats made things clear.

How is the large drop-down menu working for your site's visitors? Is there scope to improve the navigation and reduce the number of links? If the navigation is important then you can't just remove it completely can you? I would take a look at how the site is being used and how well the navigation is helping visitors find what they're looking for. What's the reason this navigation exists? Can you use the current page to provide context and reduce the number of relevant links? Once you know how important it is you'll be in a much better position to decide whether to remove it (or improve it) or not.

Hi Robert, Thanks for you response. I've resolved the issue now. I started by doing a crawl test which gave me the same number of 400 urls but revealed that they contained "../../../"   in them which seems to be something annoying the cms I'm using creates (these weren't being displayed like this in the campaign error view). I've corrected these urls and done a crawl and I seem to be clear of 400s.