Hi,
Looking at the two files, it seems like the map ‘name’ parameter isn’t being used in the one that fails. The parameter is set directly from $_POST and I see it in the request, so I don’t know why it wouldn’t always make it to the PHP code. Also, the opening “{” is missing in the failing response, which would make it invalid JSON – is that a typo or was it really missing?
I assume both requests are from the same page, so I don’t know why the data would be invalid in one request but not the other.
The logs may give some clues.
The plugin uses output buffering, so it’s possible there’s some issue there. I can give you a version of the plugin that will write some debugging info to the error log and remove the buffering, which may help. You’ll need to use the contact form to email me directly.