While not the same, my deathstix barrel has the same issue. What I do is screw the back in first and hold it tight while I screw the front in. There are probably some other ways to fix it, but I don't know them.
Yeah I tried holding the back while screwing in the barrel but the back is so small and I cant get any leverage on it. I don't think I'm going to be switching backs THAT often so would it be a good idea to throw some loctite on it? If not, I think I'm just going to contact deadlywind and ask for a switch with a regular fibur barrel