Yes, you are right, the caches make Havok Physics non-deterministic for your scenarios.
And I’m sorry to say there is nothing other than welding that can solve the problems you are seeing. Now depending on your particular scenario, you might be able to avoid some of the issues by using simpler geometry. Also, we are discussing some solutions here: Sphere collider receives strong impulse on contact with mesh collider edge
I’ll definitely note the rising need for this, and see if there are some simple ideas to get you started.