[NUC7i5BNK]

sorry its taken so long; but is still interested here is my purchase link:

 

https://www.amazon.com/gp/product/B0722N3BQ6/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

 

there are a couple of other brands with the same product, and the price has come down about $20

[Intel NUC J3455 with DS918+]

if you are referring to M.2 slot, it has to be SATA SSD  (vs PcIe)

[NUC7i5BNK]

I had somewhat the same problem, with same device.  I have had good success with the 1.04b loader as DS918+,  have not been able to  do a physical shut down thru DSM or access built-in wifi.  I'm using a vSATA M.2 SSD and 1TB hard drive in cage.  Also found a bus powered dual-drive enclosure that works with the type C connector,  powered USB enclosures work also.