To continue the bad habit of replying to my own messages, the file seems to work ok if one substitutes the_author() with echo get_the_author(). I’ll try that for now and see how it works out.
I spoke too soon, it still stops, but this time after 10 entries (still at the author-column) instead of five.
Another update: This time the script stopped because of the php-timeout values. It now runs, but takes close to a minute to list the first page of posts.