Have you tried setting the file type to DSD for the ISOs? I seem to recall a user was having a similar issue (over DLNA, if I recall correctly) which was only fixed after setting the file type.
Of course, you could always use sacd_extract to extract .dff files (avoid .dsf files, as there's a bug which causes pops at the end of files) from the ISO. That's what I did with the ISOs I have, and it works beautifully.