It sounds like the bracket that keeps the drum in place might be broken. We had this problem. The repair man could see that the bracket in one place had seared off. It was considered to be a design fault (not a wear & tear problem) so the washing machine company had to replace the drum free of charge.
There's an unbelievably large chunk of concrete in most machines which helps steady the machine so the drum can spin at high speeds without walking down the corridor. It is supported by springs / brackets. When it drops off from metal fatigure / vibration / bad luck, the machine can make a fantastically shockingly loud clunk clunk just as if you were washing a toolbox !
Any repair man would have heard of this.
Washing machines are surprisingly basic and I would expect if you / dp is careful opening it and poking around he'll be able to at least see what the problem is and then decide how to handle it from there. It might be as simple as rehooking a spring with a pair of pliers.
(Switch off mains / isolate from water, do it at your own risk yadda yadda).