Bosch logixx dishwasher?

Two weeks ago my bosch logixx developed a problem,
when it starts a cycle it makes a loud random ticking noise it lasts for a few minutes and then seems to be ok for a while,this repeats on and off untill cycle is complete,sometimes it washes ok, sometimes not.
it sound like something stuck in pump but cant see how to get to it.dont even know where it is.