Those three ideas failed, but thank you for making me look in some other directions.

I'm an idiot. I spend hours trying to find a complex solution to a simple problem.

The only problem with the two actions was using quotes ("trapper.mdl") instead of making and using a string (string trapper_model = <trapper.mdl>;)

So why did it work when the action was first? Beats me.
Why does it make a difference in this case? Beats me.

But next time I will check the radiator cap before I replace the water pump.