Im curious if this is the same issue that popped up in my Duetto's steam boiler two days ago.

There was a steady constant slight steam leak somewhere from the top of the steam boiler that couldn't be seen by the naked eye. I turned the machine off to unscrew the top and take a look, but couldn't find anything.I lowered the PID temp back to 255 from 261 where I had bumped it. It's weird, I've been able to have it at 261 for a long time before and not experience any problems.

I refilled the reservoir and turned it back on, and didn't hear the same steam leak, so I left it and went to bed. When I got up the next morning the machine was beeping, and the reservoir was completely empty.

Could this be a similar failure as described above? I was afraid to start torquing down copper nuts and washers blindly not knowing what I was doing.

Oddly, this happened 2 days ago, but now it held water perfectly fine all night last night with no noise or steam leak or any other problem this morning.

If you want to find out where an invisible steam leak is coming from, use a little hand mirror or other polished surface. Move it around until it fogs up.

Good tip. I was thinking about using some soapy water sprayed on with a litte bottle for ironing shirts, but thought I'd check here first.

Tom, i tried the soapy water, actually gas leak detector, and the surfaces were all too hot to see any bubbles, the liquid evaporated off too quickly.
I thought the leak was coming from 3 different fittings, which i tightened down before i finally realized it was the safety valve.