I have recently attempted to update from Drupal 8.2 to 8.3. After updating, all pages that use Display Suite do not render correctly. The markup generated contains a bunch of "<>" instead of the proper markup, and when I go do Display Suite configuration, all custom of fields of the node types that previously were used are do not show up in the list of fields to be placed in the layout elements. Anyone have idea as to how to troubleshoot something like this?
For Drupal 8.3.x you need to update Display Suite as well to 8.3.x (as is stated on the module page: https://www.drupal.org/project/ds).
Due to changes in core a new version is created.
- Drupal 8.2 or lower: Use Display Suite 8.2
- Drupal 8.3 or higher: Use Display Suite 8.3
Maybe that's what causing all your problems; possibly, updating the module will solve your issues.