enumeration operation may not execute

Good day! I have a user that needs to move 1000's of documents that were misfiled. She is dragging them from one Folder to another, and she receives this error "enumeration operation may not execute".. Any ideas on why or how to prevent this?

See image..

Dear Thomas Stephens! It looks like the Community cannot answer your question. That's why we have opened a Support Request with the Number SR-206741-T5N0D for you. A Software Support Specialist will contact you directly to follow up. We will update this thread with the solution as soon as we have resolved the Support Request. With best regards, DocuWare Support Team