Hi All,
After seeing the blank sitemap.xml, by doing "update cached files" or rebuilt, the sitemap.xml would be back. However, after a while, say one day, the sitemap.xml would be blank again.
It is blank on Chrome but showing stylesheet errors on Firefox. The Chrome console showed the protocol error as well. I have seen similar problems on this site and the issue from https://www.drupal.org/node/2244449. However, from what I see, the source code has already included the patches in that issue.
I have multiple websites using the same module. However, only a few of the websites are experiencing this issue. Is there anyone who has hints on how to locate the problem?