One of our clients has suddenly experienced a sudden increase in crawl errors for smart phones overnight for pages which no longer exist and there are no links to these pages according to Google.
There is no evidence as to why Google would suddenly start to crawl these pages as they have not existed for over 5 years, but it does come after a new site design has been put live. Pages do not appear to be in the index when a site search is used.
There was a similar increase in crawl errors on desktop initially after the new site went live, but these quickly returned to normal. Mobile crawl errors only became apparent after this.
There are some URL's showing which have no linking page detected so we don't know where these URL's are being found. WMT states "Googlebot couldn't crawl this URL because it points to a non-existent page". Those that do have a linking page are showing an internal page which also doesn't exist so it can't possibly link to any page.
Any insight is appreciated.
Andy and Mark at Click Consult.