The heated bed on my UM2 takes a long time to heat up. It is usually about 20 minutes to get to 95C, then an extra 10 minutes to get to 100C. It never surpasses 101 even after hours. I have heard that the early model printers, wich mine is, had loose build plate connector wires, I tried giving the wires a shake but it didn't help. Any thoughts would be greatly appreciated.