I just upgraded my project from Unity 5.5.5f1 to 5.6.4f1, re-baked Enlighten lightmapping with exactly the same parameters of previous Unity version (not using the new Progressive Preview) and I found there is not working anymore the dynamic shadows that worked perfectly fine on Unity 5.5.x.
It was a total disaster.
Why dynamic shadows are broken with legacy Enlighten support of Unity 5.6.x?
How can I get back dynamic shadows that worked perfectly on Unity 5.5.x without rollback to that version?