I know, that some LCD modules are very sensible at 'enable' input! If here the edges are not fast enough or the timing is degraded in any way, trouble will occur...... ...... Another measure to deal with EMC is to feed all the cable wires through a common mode ferrite choke (ring core for instance), where the cable is connected to your microcontroller circuit.

The ferrite will lead to further 'rounding' and in either case I would put a schmitt trigger at the lcd to 'sharpen' the signals. This will also improve noise rejection.

Erik