Rozbitý USB3 UAS po update (restartu) na 3.11.3 - SW chyby-diskuze [CZ] - Turris forum (in czech , but seems there were some bugs regarding UAS …in 3.11.x branche…, hope that linked sources will help, if you are struggling with czech , feel free to ask for quick-amaterish translate via pm ) … and openwrt ( kmod-usb-storage-uas: UASP is not working · Issue #12890 · openwrt/packages · GitHub )
… and there is also oldish thread about sata/drives issues (maybe not much helpfull in your situation)
SATA HDD issues - #66 by N0mi5 - SW bugs discussion - Turris forum
i suggest you to re-partition that drive using some live linux distro on different machine where you have full support for GPT. Somehow Turris is fine with gpt partitioning (to use them), but creating/removing gpt and partitions on larger disks can cause sometimes I/O error (using : cfdisk, fdisk, gdisk …hdparam).
...some more notes :)
… some vendors are using that UAS to provide also virtual cd-rom drive (where you have that bundled software and manual and drivers …usually very outdated anyway). Not mentioning that some vendors can have “extra” partition(s), hidden or shown as unsuported in some tools. Personally i use WD/Seagate “fancy” external drives only on Win clients.
RPI2/3 is also having similar issue like you on Turris, i am now using generic AXAGON and AKASA boxes with regular hdd inside (it costs more, but no surprises from vendor 
.
That’s another issue with those fancy boxes, inside they use (sometimes) hdd with kind of strange connectors or/and pinouts → preventing users to use those drive elsewhere.