Laravel 5.2 (using Ardent) DB query causing bad gateway error

Question

I'm in the process of upgrading a Laravel 4.1 app to 5.2 and am running into a problem with either Eloquent or Ardent in trying to do DB queries.

Our app uses the Repository model, so the problem ends up structured like this:

Controller block ($this->user is the User Repository):

if ($user = $this->user->where('email_address', '=', $this->request->input('email_address'))->withTrashed()->first())
{
    ...
}

If I comment out the "where" portion it nginx doesn't kick out a bad gateway error, so I know that's the problem.

That connects to the function in the User Repository File where User is the model class:

public function where($col, $op, $cond)
{
    return User::where($col, $op, $cond);
}

The User model is just a class that extends Ardent (a validation package that extends Eloquent). There's nothing overriding the standard Eloquent "where" function so I'm not sure what exactly is causing the bad gateway error.

Any assistance would be appreciated, if more info would be useful I can provide it, just seemed like all the relevant pieces here.