We have a Makerbot z18 printer at work and our prints have been increasingly poor in quality lately. One thing we noticed the the platen itself ( but NOT the entire table ) seems to have a slight movement left to right and front to back when secured in place. It does not appear that there is any wear on the plastic interlock parts on the platen which secure to the table, nor the red clips which hold the platen in place. All hardware appears tight as well. Is this slight movement normal ?