Parent State ID: 21
State Depth: 5
Action Taken: unstack(block_b, block_d)
Action Reasoning: To achieve the goal state, block D needs to be on block C. Since block C is clear and block D is not clear (because block B is on it), we should first unstack block B from block D.
State Description: Block A is on block B and is clear. Block B is in the hand and not clear. Block C is on the table and clear. Block D is on the table and clear. The hand is holding block B.
Action Path: ['unstack(block_b, block_c)', 'stack(block_b, block_d)', 'pick-up(block_a)', 'stack(block_a, block_b)', 'unstack(block_b, block_d)']

INACTIVE REASON: deactivated because diagram generation failed or invalid action chosen: block_b is not clear, violating the precondition for unstack.
