Trouble Exporting PDF to Server

I frequently export PDFs from INDD CC 2017.1 to a folder located on an NAS (the queue for the digital print department). It has worked fine until about two weeks ago. Now, I get the background task alert "Export" > "Failed to Export the PDF file." Saving from Illustrator, it reads "The file may be read-only, or another user may have it open. Please save the document with a different name or in a different folder." It is true for a variety of types (sizes, color profiles, transparencies. complexities, et cetera) of files. In fact, I can export anywhere else, including my desktop and other directories on the same NAS. I can also access (save to, pull from) this problem directory by other means. My workaround has been to export the PDFs to my desktop then drag them to the problem directory. It works, but I'd like to get this solved. The problem directory is a queue for the digital print department, which means I can't scrap it and create a new folder from scratch.

The odd thing is that I was able to export a PDF without bleed to the problem directory this morning, but then checked the bleed feature on and it gave me this error. I then tried exporting other PDFs without bleed. I found this was only about 75% duplicable–even when a file worked once without bleed, it was a gamble whether it would again. Still the only constant for the ones that did work was that it was exported with no bleed.

Lastly, it may help to know I'm working from an iMac and the NAS is Windows operated.

Any ideas?