At the end, when all were sopping wet, we all started emptying and dry-blasting the water blasters for storage. When I grabbed the Orca and pumped it, I saw that the nozzle valve was still leaking slightly. However, upon pulling the trigger, something felt wrong, then there was a sudden movement, trigger lost resistance, something smacked the inside of the casing, and the nozzle was more open, but now the trigger failed completely.
Upon opening the casing when I got home, I found that the plastic arm lever that attaches to the trigger rod, a spring, and the nozzle ball valve had split in half. I took some pictures (also of the Orca's internals) and am currently using some epoxy to glue the halves of the valve arm together. Will give more info on the repair progress after I attempt putting the glued valve arm back into place.
Looking at the damage pattern on the plastic arm, it seems like one half had snapped at some point while the other half shows plastic stretching, suggesting it gave away more slowly. This could explain why the nozzle valve first closed only partially before it completely failed.
