Any sugary compounds in the grease spatter? Did it soak in?
-I had a SAK that i lended ti someone who cut oranges with it in a big way, then left it to dry out thoroughly before returning it.
A complete write off. I tried soaking it for days in various liguids. Water. Citrus based brake cleaner. WD40. Meths.
Nothing worked. Several days in water woud free it up, bu all movement would seize after it dried out again.
If ever cutting sugary stuff, make sure to try to wipe it before anything reaches the joins and hinges.