Good Morning Aaron,
To resolve this behavior, on the end user's machine, please open file explorer and go the following location *%LOCALAPPDATA%\DocuWare\Desktop\DWScannerTemp*. This is the temp location where the scan files are stored before they are uploaded to DocuWare. Please delete all the files in this location. Once that is done please click the start button in Windows and type services, click on the app then navigate to the DocuWare Desktop Service, right click the service and select Restart.
You should now be able to rescan your documents that failed.
One of the main causes of this issue is AntiVirus. Please include the Scanner Temp location in your list of Anti Virus exceptions.