So I too am having this problem as well, although mine is a lot longer than 15 minutes. (I have a LS-QL4E2 with firmware 1.11)
It is on when I go to sleep, and then I get a backup warning the next morning and go to find the unit powered down.
All the auto settings for sleep, raid error shutdown, operating times, etc are disabled.
The unit can run all day (say I turn it on at 8 AM, it is still on at 10 PM) but when I go back in the morning, it is off.
My guess is something is issuing a power down command, but have no idea what. The Power Supply is not hot, the unit itself is not hot, the fan runs when needed, but is seldom actually on. I do not think this is thermal or power related as the unit stays on all day.
So, I USED to have this set to turn off at 2 AM and restart at 8 AM. I have disabled those settings in the web interface, but, is it possible that even though I have turned off operating hours settings from the web interface, and they show off now, that they are still somehow installed into the unit itself and the OFF command is still being executed? (Obviously the on command is not.) Is there some other way to access or view the internal settings?
Thanks.