Site redesign makes Moz Site Crawl go haywire

[YYSeanBrady]

I work for an agency. Recently, one of our clients decided to do a complete site redesign without giving us notice. Shortly after this happened, Moz Site Crawl reported a massive spike of issues, including but not limited to 4xx errors. However, in the weeks that followed, it seemed these 4xx errors would disappear and then a large number of new ones would appear afterward, which makes me think they're phantom errors (and looking at the referring URLs, I suspect as much because I can't find the offending URLs).

Is there any reason why this would happen? Like, something wrong with the sitemap or robots.txt?

[mrtemper]

I had the same issue. Many sub directories were renamed and  www.moz.com / www.xml-sitemaps.com for almost a week now have been throwing massive amounts of 404s. The failing links are combination of the previous and new site structure.

I also would love to know if there is an optimal way to roll out changes to minimize the problems of searching for legacy directories. And does it negatively effect a sites reputation with the index?