Check the connection to make sure it is screwed on all the way and it is clean (free from debris or liquid build up). When I put a new carto in my DCT, screwed it on and checked the resistance, it was up and down from 3.0 to 2.2. Problem was I just didn't screw it on all the way.
Another thing is that these atomizers can range in their resistance. In the factory, they may be shooting for 1.5ohms but the actual range of their product may be from 1.3 - 1.8ohms. It is also possible you got two bad atomizers.
With it working 10% of the time, it sounds like a bad connection. Maybe the type b is too big to fully screw down onto your SID. That 10% of the time sounds like when the ohm reader gets a good connection and reads accurately. I don't have any of the equipment you are talking about but thats my experience with other equipment