Maybe not all that unlikely…I just purchased a used B2301 and I found this thread as I have what I think is the exact same problem. The B2301 has had a backhoe on its whole life and only has around 100 hours. The 3PH lever does nothing (should raise the mower deck).
You say if you can move the feedback linkage and if there is no resistance, it is not connected. To try this, would I disconnect the feedback linkage from the 3PH lift arm and then move it back and forth and check resistance? Thanks.