Just saw your post, sorry for delay, all are bought from Alibaba, but as far as i know there is only one manufacturer for Ovale V8 and V6. Also it is very interesting that all my devices did not have failure and my friends just started to vape, maybe they tighten to much Cartomizers, or it is just accident.
I ordered one few days ago from smoktek and i will report here is any difference, but don't expect it soon because post is very slow from USA to my country (2-3 weeks).
I got two from SmokTek - a blue matte finish in a kit and a white shiny gloss one. Both of them are working just fine but it is of note that despite getting two of them from the same place... each has a different 510 connector. The matte blue has what I would call the "sturdy", really heavy duty 510. It's the large type connector that is "flush" with the top of the V8. The shiny white has a standard 510 connector - recessed down into the body of the V8.
The recessed connector on the white one is an accident waiting to happen. The body of the V8 is very poorly finished in that recessed connector area. There are two big gaps (holes) where the front and back seams meet together in that recessed 510 area. All it's going to take is one accident for liquid to easily get into the body of the V8 because of those gap-holes in the recessed area on the white one.
I'm just pointing out - unfortunately - that even buying two V8's from the same vendor is no guarantee you are going to get two V8's with the same type of 510 connector. And I get the idea that, in theory, these were all made by the same manufacturer. So why are there two different versions out there, being shipped to the same resellers, with very different 510 connectors?
If I had known, I would have never got the recessed connector version. But I wanted a different color than another matte blue. Then that whole ...-u-me thing happened: Sure didn't expect to get a different color, from the same place, and have it arrive with a different 510 connector.