RN 2304, lockups, ISCSI

hey all. not sure if anyone else has seen this, but i have a bunch of these devices setup as iscsi targets for NVR's and often the o/s on them will kinda lock up where iscsi connections are dropped, the UI doesn't respond anymore. only solution is to reboot and this obviously affect video recording which we rely on heavily. my readynas 6 bay desktops are between 7 and 10 years old and work flawlessly. FW's are all up to date, so I'm really looking for any ideas to possibly rectify this. no apps are installed either, ty.