Koala gem get_object returns GraphMethodException - ruby-on-rails

Question

I'm using the Koala gem to get metrics (likes, comments, and shares) on Facebook posts. I literally have not touched the Koala code in months, yet is suddenly stopped working. I'm able to get likes and comments, but not shares. I checked the docs for the gem as well as the issues on GitHub and didn't see anything related to my issue. Not sure if it's my code or the gem or a change to Facebook's API.
I have the following method, which is called by another method, which is responsible for updating all metrics on the post.
def call_facebook_api(client, method, pid, metric)
resp = client.method(method).call(pid, metric)
rescue Koala::Facebook::ClientError => e
puts "Rescue from #{e}"
puts "Method: #{method}"
puts "Metric: #{metric}"
puts "Post ID: #{pid}"
return nil
end
Here are some sample values for the method arguments:
client
=> #<Koala::Facebook::API:0x007fbbfdf25dd0 #access_token="super_secret",#app_secret="super_duper_secret">
method
=> :get_object
pid
=> "202001613484188_1142111705834093"
metric
=> {:fields=>["shares"]}
When I run the method above with these inputs it returns this error:
Koala::Facebook::ClientError: type: GraphMethodException, code: 100, message: Unsupported get request. Please read the Graph API documentation at https://developers.facebook.com/docs/graph-api [HTTP 400]
from /Users/ACIDSTEALTH/.gem/ruby/2.3.0/gems/koala-2.2.0/lib/koala/api/graph_api.rb:515:in `block in graph_call'
I've also tried the following combinations unsuccessfully:
client.get_object(pid)
client.get_object(pid, fields: ['shares'])
client.get_object(pid, 'shares')
client.get_object("#{pid}/sharedposts")
client.get_object("#{pid}?fields=sharedposts")
client.get_object("#{pid}?fields=shared")
client.get_object("#{pid}?fields=shares")
client.get_connections(pid)
client.get_connections(pid, 'shares')
client.get_connections("#{pid}/sharedposts")
Referencing the Graph API docs hasn't given me any new insights into the problem.
As I said before, I haven't touched the above code in months, yet it only recently stopped working. I did recently upgrade my Rails app from 4.06 to 4.2.5.1. I also upgraded from Ruby 2.0.0 to 2.3.0. I did not upgrade the Koala gem though. I was already running 2.2.0 (latest).