[otrs] 2.4.3: forwarding a ticket -> attachments are lost

Is this is known issue? If I forward a ticket, the attachment isn't forwarded too. Seems OK with .jpg, but .msi or .dll is missing. Is this a bug, some attachment types restricted, or a problem specific to my installation? Any ideas? I thought I read about this recently, but having done a search I can't find any info. Kind Regards, Andrew Glossop