Incorrect prop types

The error "Error! static prop using model <modelname>, which must be used on a dynamic entity." appears when the wrong prop type is chosen for the model you're using. If you use a prop_static entity, and then specify a model that has physics properties (which should be specified to a prop_physics), the engine will automatically delete the model. To fix this problem, either switch the entity to prop_physics, or change the model to one that does not have physics properties. See Prop Types Overview for more information on the different types of prop entities.