I recently got Zephyr and Stahlta in Steel Path Circuit and noticed that shooting the tornados with Stahlta's primary fire did very minimal damage numbers with no crits at all. Shooting enemies directly works properly. My Kuva Twin Stubbas worked normally when shooting enemies and the tornados.
Tested things out in the Simulacrum and confirmed that the Stahlta was not doing the proper amount of damage when shooting tornados, regardless of mod. Other weapons worked fine.