Hi,
As far As I Know, 500-599 i.e aggregate of all server errors which is basically due to servers side problems like 503 -Service Unavailable server is currently unable to handle the request due to a temporary overloading or maintenance. The reasons for these issues may vary, but you should check your server logs to see if the issues are systemic.
For Error code 400-499 like 404 - Not Found/ Invalid URL. Your server may denying access to your pages to Bingbot or there is no such content at that URL. There no action required from your side at Bing webmater Tool. You can Disallow that URL via robots.txt file method. At present there not an option to fix error by just clicking in Bing WebMaster like Google WebMaster.

Source:https://www.bing.com/webmaster/help/crawl-information-report-4ccef0b5
https://www.bing.com/webmaster/help/crawl-error-alerts-e29a3f3e

Absolutely right, Mr. Harish has answered it quite nicely.