Postgres: Error accessing parent through sibling

So here are the relationships:

class Tutor
  has_many :subjects, through: :profile
  has_one :profile, dependent: :destroy
end

class Profile
  belongs_to :tutor
  has_many :subjects, through: :profile_subjects
  has_many :profile_subjects
end

class Subject
  has_many :profile_subjects
  has_many :profiles, through: :profile_subjects
  has_many :tutors, through: :profiles
end

# the join model for Profile and Subject
class ProfileSubject
  belongs_to :profile
  belongs_to :subject
end

Now previously it was all working perfectly fine when I was using the sqlite3 database. But upon deployment to production, I'm getting thrown errors because the database is Postgres.

Here's a simple example of what I do that throws the error

subject = Subject.first
subject.tutors

And the error that is being returned is

ActiveRecord::StatementInvalid: PG::UndefinedFunction: ERROR:  operator does not exist: integer = character varying

As I understand (or was told) it means I'm trying to compare (or join) a varchar to an integer field.

The bigger picture of what I'm actually trying to do is something like Subject.where("name LIKE ?", "#{name}") and be able to find all tutors that have the queried subject. How am I able to access tutors through subject?

(I would just like to note that the associations were working perfectly fine on sqlite3)