Bug 1: Not updating path-parent correctly When detaching right subtree in access, set its pathParent.
When attaching, clear pathParent. Bug 2: Rotation parent updates After rotation, update the grandparent's child pointer.
Handle the case where parent was an auxiliary tree root. Bug 3: Reversal + lazy interaction If both reversal and lazy add are set, order matters.
Usually: apply reversal (swap children), then propagate lazy. Bug 4: Forgetting to splay after findRoot The leftmost node traversal doesn't maintain amortized bounds without final splay. Bug 5: Link checking Ensure nodes are in different trees before linking. Link on same tree creates cycle.