Suggestion:
Check endurance to let it dig or not when endurancemoodlelevel > 3.
I check the way to found worms in that action it's too easy.
IsPlowAction.lua
Reducing endurance when dig the floor
Maybe add sandboxvars.natureabundance in the code to control ZombRand() chances to find them.
With that system i think players can't farm worms too easy.