A volume element (voxel) printing system for printing a three-dimensional object includes a first printhead group having a plurality of first printheads configured to print a first voxel layer on a substrate; at least one second printhead group having a plurality of second printheads downstream from the first group, the second printhead group configured to print a subsequent voxel layer on at least part of the first layer, said second printheads being reconfigurable as backup printheads for the first printheads in case of failure; a conveyor configured to convey the substrate past the printhead groups; and a control system configured to control and monitor the printhead groups, the object insertion device, and the conveyor, and dynamically to reconfigure the second printheads upon detection of failure of a first printhead. The at least one second printhead group is vertically spaced from the substrate by a greater distance than the first printhead group.