When modelling an embedded pile directly connected to a plate (with an interface at the top and/or bottom side) the embedded pile and plate are not directly connected: the interface also exists between the embedded pile and the plate. As a result the plate and embedded pile may undergo different displacements.
If a piled raft is modelled using embedded pile and the raft has an interface underneath to model the interaction between raft and pile, this interface is also present between embedded pile and raft. Hence, the embedded pile is not directly connected to the raft while it should be. This makes the piles behave very soft and will influence the ratio between the forces carried by the raft and the soil in favour of the soil.
Possible work arounds:
This is fixed since PLAXIS 3D 2011.01