Salesforce Sync Error: No XML Document Error

[nzegarra98]

Hello, 

I received a Marketo Salesforce Sync Error that myself and my team are not familiar with. The error is as follows:

I was able to find one post about something close to this error, but their issue was with a specific to a lead sync issue, based on a problematic character. You can find that thread here: https://nation.marketo.com/t5/product-discussions/lead-sync-error/td-p/64235

I have ran a test and can see that we are syncing new and existing leads with no issue. I was wondering if anyone is familiar with this lead, and if any action is even needed. 

Thanks!