It's not a problem with the LHB coaches, but with the CBC couplers. CBC couplers, are by design, far more safe and easier to operate than screw couplers, but it is difficult to avoid the jerks when using CBC couplers. To a large extent, these problems have been solved worldwide, but still, screw and buffer couplers, have slightly better ride quality as far as jerks are concerned.
IR too tried out modified CBC couplers on trains like SC-LTT Duronto (LHB coaches) and found satisfactory performance. In time, all future LHB coaches will come with these improved couplers.