Sorry all for my late reply on this.
I talked to both my SF developer team and DevOps folks. The issue is due to a timeout when Marketo can’t get a response back from Salesforce. Unfortunately, as a Marketo user there is nothing we can do to fix it. We have to wait for Marketo to address the issue.
Bringing this one back up, is this still an error that we should be experiencing, or has Marketo already addressed it? I'm still seeing it on our end.