Most times I collect several FTP files in a collection for later copy. Afterwards I copy the collection content to my local system. This works very well but if using a collection as source files the FTP resume operation can't be used for existing files (that exist in the destination from a previous aborted transfer).
@ Leo / Jon: Can you confirm this problem?
Thanks for the report, we'll look into it.
This should be fixed in the new 10.5.2.4 beta.