Strange error in status reports en unable to safe my taxonomy term url-alias When I go to admin/reports/status I see this error (see image).

Also I am unable to safe my taxonomy term url-alias? What does this error mean and how can I fix this?
You can safely ignore this.

See https://www.drupal.org/node/2661178 and the core issue linked there for details.

Nothing is broken, the entity definition change tracking just gets a bit confused.