Rafts used to work very well for me in V3.1.
In V4, the first object layer appears to be much less filled than previously and sometimes, strands are ripped out of the layer and stay with the raft upon removing the latter.
So here is what happens:
The first layer is dropped onto the raft from Z=(separation distance + layer height) in order to decrease adhesion. The problem seems to be that the second object layer is the extruded from Z=(separation distance + 2x layer height), i.e. the extra height is maintained, leading to poor adhesion between the first and the second layer.
Now if I define two processes, set them switch over between the first and the second layer, and set a Gcode Z-offset of -(separation distance) for the second process, the second layer is extruded at Z=(2x layer height). The outcome is much better and I wonder whether it shouldn't be that way in the first place. (Maybe a bug intruced in V4?)