Dishwasher smells like fish

There are several possible causes.

First, make sure the machine is properly installed with the drain hose up in a loop or an air gap before going down to the drain. This is to ensure no dirty water or smells from the sour or garbage disposer backs up into the machine.

Sometimes nasty stuff gets trapped inside internal parts of the machine and inside the sprayer arms. It is normally easy to remove the sprayer arms for cleaning, on reasonably modern Bosch machines they can also be opened up for easy access.

There are also special dishwasher cleaning agents that you can use to perform periodic cleaning cycles. Some believe it is important to use rinse agents to minimize the problem, maybe it is worth trying if you don't use it.

If there is warranty left on the machine I would advise you to complain, there is a slight possibility there is something wrong in the machine for instance bad choice of insulation lining that have been known to emit foul smells.

Good luck with tracking down the cause of this!