Ok, I figured out what's causing it.
The bridge is JMS561.
OMV pulls this for all drives when the Devices tab is clicked.
smartctl -x /dev/sda -d sat
Running this manually I can also crash it.
Specifically this:
smartctl -l devstat /dev/sda
crashes here:
root@openmediavault:~# smartctl -l devstat /dev/sda -d sat,12
smartctl 6.4 2014-10-07 r4002 [armv7l-linux-4.9.30-odroidxu4] (local build)
Copyright (C) 2002-14, Bruce Allen, Christian Franke, www.smartmontools.org
ATA_READ_LOG_EXT (addr=0x00:0x00, page=0, n=1) failed: 48-bit ATA com