Version 1.3.0 "sendMessage" doesn't return information about the message

I've a project that relies on the returned timestamp from sendMessage. I wasn't able to discern easily what's causing the issue, but this is what I've found so far:

With 1.3.0, the object that is return appears to be empty:

handle = {SlackMessageHandle@4518} 
 messageId = 0
 slackReply = {SlackMessageReply@4535} 
  replyTo = 0
  timestamp = null
  ok = true
  error = null

Downgrading back to 1.2.0, it populates correctly:

handle = {SlackMessageHandle@4456} 
 messageId = 1
 slackReply = {SlackMessageReply@4474} 
  replyTo = -1
  timestamp = "1634492783.007600"
  ok = true
  error = null