Yesterday I noticed that the rear end of my Enertia Plus was wobbly. On closer inspection I saw that a bolt is missing. In the time that I own the bike (a year and three months) this is the second time a bolt's fallen out.
I've already asked my dealer about the size of replacement bolts, but with @shinysideup's
scary story about his tail nearly falling off in mind, I think another warning can't hurt:
check to see if these bolts are still fastened regularly! There's four of them; two on each side under the taillight. Arrows mark the ones that had gone missing on mine. The bottom one I could replace with something I had in my toolchest, but the one that's missing now must be shorter and you'd need some L-shaped wrench to screw it in.