From mail list:
It looks like it's the history potential gridding. Note that 3-dimensional order parameters take a very long time to converge. If your doing free energy simulations it's best to keep the order parameters to 1 or 2 dimensions.
and a thermostat should be added in the car-parrinello block
e.g.: nose-hoover 1200.0 300.0 1200.0 300.0
by
Eric J