Have a SEA PLC problem

Hello, I have a project used the SEA PLC(used the twenty years)the models are D4110(master) and M4012(slave),now the D4110 is display the communicaton fault.I check the D4110 and M4012 ,they are via serial network communication, the D4110 current network address 1: 1,the current network address 2: 2,the M4012 current network address1:2, then by laptop and RS232 cable online monitor the M4012, the M4012 no fault,online monitor the D4110,the D4110 no internal fault,but have a communication network error,the error code is 0EH description is transmit collision detected(port#1),please guide me, thanks! the attach file is project program.