Definitely want to stay with the 14mm. I'm pretty heavily invested in TD wheels, be it buggy, SCT and ST. Being a V3 kit, it came with the 12mm front and rear hex conversion. But I chose not to go that route. I had no issues with this until I installed the proper axle with the new multi-link setup included with the V3. I have read both the DESC210 and DEST threads when I picked them up. These threads are outstanding to get a good picture of what fails, what should be upgraded and what to watch out for. One post is usually not super helpful with this, but over the course of five hundred posts, a pattern usually can be seen.(yeah, I'm a dork lol)
I do have some TD alloy hexes left over from the DESC210 rebuild I did recently. I always restore a car to box stock when I do it so I can choose what needs upgraded. Locking hexes would solve this for sure. The way TD does it, the hexes don't push against the pin....makes zero sense but anyway. I've already installed the shims, .04 worth on the rear. I'll have to take it apart again and have a really good look at it to see why it's only now happening and not before.