The feed produces error when $this->updated_at is changed to a column name other than 'updated_at'

[UnrulyNatives]

I am trying to customize the code in my Model. Now, according to your docs, there is a line responsible for declaring publication time:

->updated($this->updated_at)

The issue

This field is updated when modifying description or updating audio filename.
Any change to the episode entry causes the feed to loose the intended order sequence. (The recently updated entry is moved to the top of the RSS feed, which should be the newest episode.
Hence I have a custom field emited_at to declare the initial publication date of a podcast's episode.

However, when I update the line with ->updated to

->updated($this->emited_at)

The RSS feed produces an error and/or does not pass RSS validators.