I received my 4nine (love it) ... First thing is make sure that you are using a top device that has a 510 pin that extends at least 1mm (min) beyond the 510 threads. This is a must, not a negotiable. Do not use any RDA or RBA that has a flush 510 connection pin as it will short out.
Also, its sounds like you are using a flat top battery with the 4nine which is not recommended. This mech was intended to be used with nipple top batteries, not flat tops which can cause a short. There are some people who are ignoring this recommendation, but I would not do that.
I am not having any issues at all with my 4nine, it vapes just fine, no shorts, no hot buttons ...