Cannot save/export reports after upgrade to 3.5

If you are an upgrade user (upgrading from 3.0 to 3.5) and experience this issue on MP, There are 3 things might cause the issue;

1. directory permissions (/var/cfengine/httpd/htdocs/api/static) should belong to apache:apache and has 0755 permissions
2. disk full
3. wrong path in mongodb (if upgraded from 3.0 for example). Need to fix with mongo command. (mp_install_dir)

$ /var/cfengine/bin/mongo
$ use cfreport
$ db.scratch.find()
$ db.scratch.update( {}, { $set: { "mp_install_dir": "/var/cfengine/httpd/htdocs" } }, false, true)