User 1 moves X from A to B
User 2 moves A.getParent() from A.getParent().getParent() to C

A is read locked, B is read locked
X write locked

A.getParent() is write locked
A.getParent().getParent() is read locked
C is read locked

For some reason, user 2's request is faster:

A.getParent() is moved

User 2's request is gets now processed further

G2 tries to move X but it's file location is no longer valid because X.getParent().getParent() has been moved