Most models nowadays define the tightest curve on which they are suitable - I infer that you are trying a tighter curve than recommended. Are you using tension lock or scale couplings? If the former, as the distance between vehicles is over scale anyway you could add a loop of wire to connect the loco coupling hook to the next vehicle's coupling hook. That is, increase the distance to the next vehicle slightly. Not ideal, but you aren't in an ideal position!
Edit: sorry, the problem is in N gauge. I thought the Dapol 50 was 00!