I have 3 of the 5 you mentioned (Snow Wolf, X Cube II, and Tesla 200w). I'm selling my Tesla. It's ok, but I had problems with some of the lower builds on it. It just didn't like them. The Snow Wolf and the X Cube II would read them, but the Tesla didn't like them. I'm talking about .12-.09. Snow Wolf fires it. The X Cube II will fire it. Haven't tried SS or Titanium on the X Cube II though. It's TC is wonky to me as well. Not being able to change the power makes it difficult to dial in that perfect vape. I like warm vapes as well and I can't really get it there no matter how much I turn up the damn temp. The Snow Wolf just works. The drawback for that is no ability to upgrade and you are limited to just nickel. The Snow Wolf feels the best to me. The glass doors make me nervous about dropping it. The X Cube II battery door isn't that secure and annoys some people during use, but it doesn't really bother me. Overall for value, the X Cube II is the hands down bang for the buck ($64 when I got it). Ability to upgrade and the available wires you can use right now will be hard to beat. If it breaks, you can buy another for the price of the Snow Wolf. I have no experience with Sigelei or the IPV4. Hope that helps...
And on the OP original topic, I had that same problem too after the firmware upgrade. Took out the batteries and restarted it and it has worked fine.