alright ive been struggling with this for a few weeks, i have a play, upgraded its bed size to 12"x4"x5.5" LWH now recently what was happening was that on long/tall prints my machine would start skipping about an inch up and progressively get worse as it went. its the motor not being able to push/pull its not slipping on the cog. i cannot find anywhere in the Cura command box to tell it to send more power to the motor to compensate.
i used 1/4" aluminium plate, with 2 6" heated beds under it. its already fairly heavy but cant be much more then a plus bed. if anyone knows the plus info maybe i can tell it its a plus and change its bed size