SMS native plugin always invokes error handler with `OK`

I am using the native SMS plugin to send a message to a single user:

return SMS.send(cells[0], message) // send to first
   .then(() => this.sendSMS(message, cells.slice(1))) // send to the rest
   .catch(err => {
      console.warn(`Error sending SMS: ${err}

This works. However, it always invokes the error handler with simply the message OK. This makes me think there’s something wrong with the error handling, but I can’t see anything which is going wrong. I thought perhaps the plugin wasn’t decorated correctly:

], SMS, "send", null);

but I added entries for successIndex and errorIndex and got the same response. For the moment I’m just ignoring if the error returned is OK. Has anyone else hit this?