Having the same problem with my Rome Mod Rocker and Flux Bindings. It's still a newish board so I doubt/hope it's not the inserts. However after years of hearing or being told that all boards have the same screw insert depth and it's the base plate thickness that effects the screw length. I decided to check with my old Burton and Capita boards. Turns out the Burtons insert is at least 2mm deeper than the Capita insert.
I'll measure the Rome insert and the Flux base plate depth tomorrow and buy the appropriate size screws. If they stay fixed tight I'll repost for any other poor bastards like myself and OP having the same problem.