IOS ModifyEvent not working for Calendar plugin

[MrShakes]

I am using the calendar plugin and sometimes the modifyEvent returns an error with just a string of characters that look like an ID and other times nothing happens, no error or result, IOS 10.2.1.

System info:
Cordova CLI: 6.4.0
Ionic CLI Version: 2.2.1
Ionic App Lib Version: 2.2.0
ios-deploy version: 1.9.1
ios-sim version: 5.0.6
OS: macOS Sierra
Node Version: v5.7.0
Xcode version: Xcode 8.2.1 Build version 8C1002

Code:

$cordovaCalendar.modifyEvent({
    title: 'Space Race',
    notes: 'Bring sandwiches',
    startDate: var,
    endDate: var
    newTitle: 'Ostrich Race',
    newNotes: 'Bring a saddle',
    newStartDate: var,
    newEndDate: var
  }).then(function (result) {
    // success
  }, function (err) {
    // error
  });