I just finished building an Ultimaker Original+ and am having some issues with the Y axes movement.
When moving the Y axes, there are loud grinding noises and the movement along that axes is inhibited. I have made sure that the sliding blocks are on opposite are level with each other and have also tried adding some oil to the left Y axes.
Moving the printer head along the Y axes by hand when the machine is off is also very hard. The X axes moves easily, but the Y axes feels like it is getting "stuck" at certain points along the way. I recorded a short clip of this is action. :(