The word export functionality from the issue navigator does not export correct documents. This occurs in my local installation as well in my customers installation as well in your current jira.atlassian.com installation. It doesn't matter if the result list contains just 1 entry or several!

The word export from the issue detail page works fine.

Since the document file-size looks reasonable (e.g. about 500k for 150 entries) it seems that just the generated html content is corrupted. When you open such an document (see attached export from your jira.atlassian.com installation) not even the first entry will be displayed completely.