Help understanding why writes are extremely slow

I'm moving about 1tb from an ssd to my array and am seeing 250KiB/s write speed.

Hardware config:

TeamGroup 2TB ssd -> StarTech SATA III to usb3.0 cable adapter -> Ugreen DXP4800 Plus usb3.0 port -> 12TB disk (with parity disk, no cache)

Settings:

• turbo write enabled
• Parity enabled (this data is too valuable to turn it off, but I figured I should still get write speeds much higher than this regardless)
• Unassigned Disks + Krusader UI is how I'm transferring the files

Anyone have any idea why my write speeds might be so low, or how I can troubleshoot? Everything is brand new except for the source ssd. The SATA to USB cable advertises itself as being 5Gbps. I'm also noticing in the Krusader file transfer window that the transfer reads "stalled" pretty much after every file.

I'm pretty new to unraid so maybe there's some basic setting I'm missing?