Reference.push failed: first argument contains undefined in property 'post.global.5c663456-01bc-4ea2-aed0-9b47ef95bb9e.creator.na' code example
Example: [Unhandled promise rejection: Error: Reference.update failed: First argument contains undefined in property 'orders.-MN6f-JxMnLS4qAmVfs0.info.other_phone']
to make sure your object does not contain any undefined props use this simple trick:
JSON.parse( JSON.stringify(YourJsonData ) )
For more info take a look at this codePen: http://codepen.io/ajmueller/pen/gLaBLX