Even though you are preloading, you are still required to explicitly use joins when filtering and ordering on columns on other tables. Preloading is used to eagerly load the data to map into your models, not to join tables.
Chain on something like this:
.Joins("LEFT JOIN rfm.robot_models AS robot_models ON robot_models.id = robots.robot_model_id")
I'm not positive if you can use the
AS keyword using this technique, but if not, it should be easy enough to adjust your query accordingly.