What does your update code, model, and db table look like?

Model:

class MonthlyUpdateStatus extends Model
{
protected $table = 'monthly_update_status';
protected $primaryKey = 'date';
protected $guarded = [];	
}

DB Table:

+------------------+------------------+------+-----+---------+----------------+
| Field            | Type             | Null | Key | Default | Extra          |
+------------------+------------------+------+-----+---------+----------------+
| date             | varchar(255)     | NO   |     | NULL    |                |
| step             | int(11)          | NO   |     | NULL    |                |
| created_at       | timestamp        | YES  |     | NULL    |                |
| updated_at       | timestamp        | YES  |     | NULL    |                |
| type             | int(11)          | NO   |     | NULL    |                |
| id               | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
+------------------+------------------+------+-----+---------+----------------+

Code:

$updateStatus = MonthlyUpdateStatus::where(['date' => $dateNow, 'type' => 1])->first();
$updateStatus->step = $nextStep;
$updateStatus->save();

Result: If I have in the table more than one record for this date (e.g. with type=1 and type=2), all will be updated with step=$nextStep.

Your table shows id is the PK, your model has date as the PK. They should be the same.

Yes, that was the problem. I had made the id to be the PK in the Model and it has started working correctly. Many thanks for the help!!