In the example you sent, there are multiple \r\n instances in your base64. Is this something added when you were saving the JSON to a file or was it part of it before? If it is part of it then most likely that is the problem because the string will be cut off at the newlines leaving you with an incomplete base64 string.
Other than that, we've seen when you add a TMS FNC WX component to your web form, an extra empty script tag is added to your project.html.
Make sure to remove this extra empty script tag, we'll investigate why it gets added in the first place.