From what I can see... there is a bubble on top which is most likely the light...
I've used Stealth Heaters for a lot of years and have had overall excellent success with them. I haven't had one overheat a tank and the only one I've had fail was easily replaced by the manufacturer.
I can't speak for every stealth failure out there, but I do know a lot of them I've followed I considered the failure due to user error more so than product failure...
Just to toss in, I still think they suggest using more W per G than necessary and that using more W per G than necessary can harm the heater...