To answer your post topic question . . yes, I've replaced the braid in my mash tun . .It's simple and quick, and I did it because I reconfigured my manifold slightly.
Questions for you . . How big is the barb?(diameter) Are you using a single length of braid? How long is the braid? What kind of vessel are you using for your MT?
The thing that causes braid to contract is being stretched. Something is pulling on it to make it pinch at the barb. Perhaps a longer piece of braid would lessen the potential of tug stress. Or make a loop with a "T" to have 2 points for the wort to enter.