We had one the other day as below:
QDSMain.Exceptions.TaskFailedException: Task execution failed with errors to follow. ---> System.ArgumentNullException: Value cannot be null. ||
Parameter name: stringToUnescape || at System.Uri.UnescapeDataString(String stringToUnescape) ||
The good news is we figure out that a previous employee had created the credentials on his local login which had expired since leaving the company.
So keep an eye out on the processes on the hosted server!