Get some idea about type of sitemap error from Google: https://support.google.com/webmasters/answer/35738?hl=en
These error/warnings will never come back again if i fix it. This type of error generally show only on some wordpress based site because of custom posting format.
Please note, for $5 i can remove 5 error/warnings. If your sitemap have more than 5 error then please contact with me for a quota.