I have 2 UM2's and when I use the multiply function and attempt to print multiple objects at once the first print sticks, but the 2nd print does not. I assume that is because the glue has already cured or hardened making it difficult for the print to stick.
With my Makerbot my prints would always print layer by layer, instead of object by object, so I never had this issue.
Anyone experience this? Or have an idea on how to fix it?