jac, sorry to hear your having these issues with the Gold V2. I can't be of a lot of help other than to say I have used many of them and never had a problem.
It sounds like the threads on the carto you were using were not cut correctly and this possibly made it difficult to put the carto on your 510 vaping device.
Going to the adapter was a good idea, but if you do this and find it is hard to get the carto off of the adapter, you can leave it on there and go ahead and refill the carto. It won't hurt anything. I do it from time to time.
Then just get it off when its time to discard the carto and at that time it won't matter if it comes apart.
TT