A single Efest flat top 18350 did not rattle for me before I replaced the wimpy spring on my chrome VAMO. The 18650 didn't rattle but would periodically disconnect.
However, if you have the spring pictured on the right you should not use your VAMO without testing with a multimeter to see if the resistance is OK or replacing the spring.
The springs listed below are the same springs. Mine work fine and others have also reported them working well. If you need a spring get while the getting is good as they tend to run out of stock.
Hot Spring - Silver Bullet / OmeGa
HeliX hot spring
Silver Bullet/Omega - Replacement Hot Spring
You can contact your seller for a replacement spring but Health Cabin in China just announced they will be sending out replacements to their customers. That means it will be a little while before vendors not located in China will have replacements available to send to their customers.