If you try to take too big a bite or lift too much the excessive pressure will trip the pressure relief valve causing an unmistakeable squealing and ofcourse it will not lift the load. No damage done if you back off but, if you continue to overload the system something will eventually give, like a line may blow or damage could occur to the pump assembly.
It's very easy to go into overload when digging, when it happens just back off and take a smaller bite.
Volfandt