Yesterday I was trying to import a GPX file into a WordPress post on a site running my Routes plugin for WordPress. The post had several images that had been inserted using the WordPress media library, and the GPX import failed, without telling me what was going on.
So I added some messages to show on the screen when you save your post, and that led me to understand what the problem was, and I fixed it. So I just released version 2.2.10 of the Routes plugin. Upgrading is advisable.