String could not be parsed as XML

[gbrits]

Hi there @danicampora / crew,

I'm using a slightly outdated version of your plugin - it cannot be updated due to custom changes made to it for custom taxation criteria on certain products - but occasionally, on the automatic trigger for sending invoices to Xero when they are Complete it is returning the error: String could not be parsed as XML -- when the exact same invoice is manually sent it goes through without an issue.

Obviously I understand you can't support me much without being able to get into my code and you could dismiss it as having been customised / edited so you can't support it -- but if you could just point out which method / class is responsible for this automatic call I can try to debug the OAuth call myself - because I imagine it's the OAuth that is hitting a hurdle / timeout and just needs a try / catch scenario of some kind.

Thanks for the help!