undefined method `attribute_method_matcher' for "":String first THEN NoMethodError: undefined method `has_key?' for nil:NilClass

Hi I am working on a project via ruby on rails.

I have my model defined as hkn_int.rb and point it to field_database table

So when I in rails console, and type HknInt, it gives me the details about the table, and I type HknInt.count, it also gives me the number of items in the table, but that's the only two commands I can do without an error.

If I type HknInt.first, it gives me

undefined method `attribute_method_matcher' for "":String

Then I type it again HknInt.first, it gives me another error

NoMethodError: undefined method `has_key?' for nil:NilClass

It is just weird. When I put the code on another server, it works fine. But all the configs are the same, should make no difference.