Can you please try the following steps:
1. Look for any running workflow instances here: <host:port>/libs/cq/workflow/admin/console/content/instances.html
2. If there are any entries, terminate them.
3. Try uploading the asset again.
4. If the issue still persist, try disabling "Smart Tags" workflow from here: <host:port>/libs/cq/workflow/admin/console/content/models.html