Moving screenshots does not work properly

We have problems with screen shots when moving issues to another project. Our end users enters issues to one project. We at IT reviews the issue and moves it to another project and include some additional information. A really good feature is the screen shots, which our end users can attach.
We are now experiencing problems with this functionality:
1. When moving multiple screenshots not all screenshots are moved properly. At least not the thumbnails.
2. When trying to remove those moved issues we are getting an error:
Exception removing issue: com.atlassian.core.AtlassianCoreException: Error in action: com.atlassian.jira.action.issue.IssueDelete@1f96e63, result: null

Our version (which you probably know anyway) is: Professional Edition, Version: 3.3-#96