Import photos save 2nd copy issue

Running LR Classic and have my 'Import photos' configured to save to a local hard drive and make a 2nd copy to my local Synology DS218 network drive - the imported image files are being saved to the local hard drive but NOT to the network drive- if I direct the 2nd copy to another local hard drive that works.  Can you help me understand why LR won't seem to save the 2nd copy directly to my network drive?  Thanks/Bill