If it's auto firing, it is a safety concern and I would not continue using it.
Mine started doing the exact same thing about a week ago. It is totally unreliable. for a while, I thought I got it working, took a few vapes, then set it down on the table beside me. About 10 minutes later, it started hissing...it was auto firing on it's own without me even touching it. I think it's a defective pc board. Since I bought it from Fasttech, and I know that Cloupor won't accept any returns from items bought from Fasttech, I cannot send it back to Cloupor. So, I decided to open it up and take a look.
The first thing I checked, was if it was a defective switch. I opened the device and took out the buttons. I manually connected wire to the pc board touching the button contacts, and it would still fire for 15 seconds. So, the problem is not with the button, but the pc board.
The PC board is loosely in there, it's not screwed in. It has two slots that hold the pc board in. They put a heavy amount of solder on the 510, probably to keep the 510 connected and put the wires to the 510. Then they put a huge glob of a rubbery substance around that solder, probably to keep the wires from moving. I'm not complaining about how it's made, just that it makes it difficult to replace the pc board.
One day, I might buy another pc board and 510 and attempt to fix it. It looks like it has the same setup as a Yihi board. I think just this pc board is defective. It's a shame too, since I loved the device and it was my main unit for a while and preferred the aesthetics and feel of it over my Sigeli (which I am using at the moment) I would say do NOT use it, since any mod that fires on it's own is dangerous, and will ruin your coils.