If you update a puppet class to remove an existing class parameter which has been overriden by foreman then the agent will fail with an unknown parameter error.

To reproduce:
create class with a parameter
import class into foreman
set class parameter to 'override' (smart class parameter)
remove parameter from class file
import class into foreman
run agent

The agent run will fail because foreman is still passing in the old parameter and the updated class is not expecting it.