I've experienced that, although, I had mine on a Unotch. This was before they put the disclaimer on the website that the extensions don't work with Unotch. In fact, I think my angry email about it spurred the disclaimer on the site, as I told them specifically there were no compatibility notes or warnings for buying. It magically appeared the next day.
But for the uninitiated: Unotch are not full metal lined. The entire mag body flexes with loading and as the center bulges, the top and bottom narrow. As the bottom narrows, it loosens in the extension well. One good bump and the extension comes off. The spring tension jettisons the entire contents of the mag, rounds, follower, and spring.
The TT ones look great and are machined nice, but the simple retention pin method of securing them on the magwell to prevent slide off is too simplistic and allows for too much play. I suppose they would be fine on full metal lined mags, but that means square notch if in MA. If you're in a free state, then the should be fine then. Although, while not nearly as aesthetically pleasing, I find the Taylor Freelance extensions much more robust in terms of securing them on the magwell with a solid plate held in by two screws. No play at all once attached. Got to thank fred2386 for showing me those.
