Send it back to ACK! I had all of the same problems and the same response from ACK. If it is an experimental it must be you. It's not.
I went for months with it off and just carried my PLB as I expected nothing but pushback from ACK.
I heard of someone at the local airport that had the same problem, sent it back and it has since worked fine. I finally sent mine back and asked them to inspect it as it would go off in flight from thermal activity with nothing but the antenna connected.
I got a message back from them immediately saying they were installing a new updated circuit board. They asked that I give them feedback.
I originally just armed it and did not connect anything but the antenna. It worked! I was able to fly for hours in thermal activity with no activation. For the last two flights I connected the remote and it worked fine until yesterday. In some minor thermals it went off. No other activity other than the radio. I do not have it connected to GPS. I was able to turn it off at the remote. So I would have to say it is much better, but still much too sensitive.

Stop taking their BS and push back. They have an ELT that is entirely too sensitive. There are stories all over the internet with people having the same problem.