Well that definitely rules out Nozel and Lil considering Liar is already inside of the base. It seems Nozel's odd behavior just stems from him holding a personal grudge for what they did to Fuego. Most likely candidate at this point would be Dorothy, but I always considered to be too much of an obvious choice.
The difference in translation between JB and MS is interesting in regards to what the guy who Luck beat up was saying. The former translated it as him being 'chosen', which I originally interpreted as him merely being arrogant. However MS talks about him having received a new name, which fits with the idea that some of these members have dual natures. Though the fact that it seems he got one-shotted it might just be nothing.