Heaven's Gifts is a Chinese retailer that is not very reliable. If they do manage to get your order out quickly, it comes on the slow boat from China so it takes a few weeks.
I have yet to find a 510 connector with snug threads. Though, I have a stainless steel
mod from Puresmoker with tight threads. That's the only one I've come across, but the threads are cut into the mod itself. It doesn't have a connecter per se.
Sor far, every connector I've used for mod building has loose threads to start. Then they proceed to loosen up completely to the point of failure. Some are better than others. I've bought a few lots of the various press-in type connectors from Madvapes. Some are tighter, but none are snug. Doesn't matter anyway because they all wear out on me eventually.
Bstedh here on the forum is working on a connector that may resolve these issues. It will be stainless and have the option of flush or standoff mounting so that's good. Not sure how it's going at this point but if it happens, he'll do a co-op.
Here's the thread.