All of the hydraulic components in a waterjet are subject to wear: hoses, connectors, etc. The nozzle is considered an item that you simply have to replace regularly, kind of like windshield wipers on a car.
The pump is one of the larger and more expensive components of the waterjet cutting system and also tends to fail at inconvenient times.
Well, as a student that makes martian rover analogues for University Rover Challenge (7th place, woooo) I can attest that there is failure at the most inopportunate time.
Our unis water jet crapped out right before we were to have final parts cut on it before sending them for competition. It was massive PITA
That's actually pretty bad because you have no idea whether it's still going to explode. Like a firework that does nothing after the fuse burns into the casing.
The alternative is worse for everyone but the bombers. I very much prefer to have a bomb in the mall that might explode any moment to one that actually just did.
It happens when you turn it on since a sensor or self-test detects it. Failure was inevitable but conveniently prevents you from wasting time and money on that run. I know this kind of thing can happen with some kinds of equipment but can't speak to if these could detect failure early. Works with many types of equipment, including computer software and hardware.
The pump is one of the larger and more expensive components of the waterjet cutting system and also tends to fail at inconvenient times.