PDF Services API - pdftoimages endpoint throwing error "Unknown error performing transfer"

I am trying to extract a pdf as individual images, and had the process working on Monday, but yesterday and today the endpoint is returning an error when polling for hte status of the job. Error is below. All other functionality is working (generating access token, requesting assetID, putting asset, executing job pdftoimages) - I've even verified that the pdf I'm placing as the asset is a valid pdf. Any insight into this error that may help?

{
"error": {#13165
"code": "INTERNAL_SERVER_ERROR"
"message": "Unknown error performing transfer"
"status": 500
}
"status": "failed"
}