I have had this before on external drives. I know the solution for this is to create an empty folder in the directory and then delete it, and usually that solves the problem. However, this time it's not so easy. Mainly because I am now using a Synology NAS system, all my RAW files live on there and I can not for the life of me figure out how to get rid of the message below :
Delete Permanently? 1 of these files could not be moved to the Trash. The files are on a volume that does not support Trash. Would you like to permanently delete them?
Has anyone ever had this issue before, with using a Synology NAS?