One slash, 123 addresses out of line

I submitted the sitemap to the search engine. It carries 123 addresses. I opened one of them directly and got a 308 back. The next one too. All of them.

I have the setting that ends every address with a slash, so the real address is /ko/. But the code that builds the sitemap was writing /ko.

There is a reason it stayed out of sight. The canonical tag and the per-language alternates already ended with a slash. Open it in a browser and nothing is wrong: the redirect quietly takes you there.

A crawler sees it differently. If every address you submit bounces one more time, it gets filed as a page with a redirect and indexing slides down the queue. All 123 were in that state.

The fix was one line. Finding it was not.