This can occur if the cable is disconnected after an AUX command is issued, but before the reply has been received.
This is a known problem with the DisplayPort v2.3 and v3.1 that has been resolved in the DisplayPort v3.2.
To work around this issue, send a dummy AUX request after the disconnect.
This will ensure that the state machine recovers from the "stuck" state.
Please see (Xilinx Answer 33258) for a detailed list of LogiCORE IP Display Port Release Notes and Known Issues.