The build up of wire on one side can be caused if you do not have your Zero set correctly. When testing , we placed a thin metal ruler in between the felt pads, jogged the feed to the edge of the bobbin and set zero. If you are happy your zero is set correctly then either reduce the height of the pickup or decrease the wire size. Wind a few layers to test and see if it is shaping up as you require. Some people using the ruler will first set their zero and then jog the feeder to the right hand side of the bobbin, make a note of the feeder position and set this as the bobbin height in software.
Also one thing that catches people out is that they do not allow for the coating on the wire that can make the wire diameter larger than what is written on the wire spool. As rule of thumb allow 10-15% for the coating when setting your wire size.