PDF Library error

Hello,

Since August 6th,  a package creation request that we haven't touched in months started failing with this error.  It happens only in the sandbox environnement, the same request works correctly in production. I've reviewed the release notes for upcoming changes but nothing seems related. Is this a know issue?

{
   "name": "Validation Error",
   "message": "The number of Pre-Verify results does not match the number of documents that were sent for verification.",
   "parameters": {
       "errorException": "PreVerifyDocumentCommand : (DE) Code 6 - PDF Library threw an exception with error message [Expected a dict object.]. "
   },
   "code": 400,
   "messageKey": "error.validation.documentPreVerifyInvalidResponseNumberError"
}