how to fix collisions when movement is too fast?

I'm not sure if this is the problem, but you perhaps shouldn't be using Translate, if you are. Use some kind of Lerp or something, look it up in the docs. Hope this helps.

Thanks. I could have made it clearer, but I'm using RigidBody.MovePosition, so that shouldn't be an issue.

Have you read the description on RigidBody.MovePosition?...

For kinematic rigidbodies it applies friction based on the motion of the rigidbody. This lets you simulate moving platforms with rigidbodies sitting on top of the elevator. If you want other rigidbodies to interact with the kinematic rigidbody you need to move it in the FixedUpdate function.

...Have you tried using any other ways, like Lerp, etc.?

Yep - read the description. I find it a little confusing, but the part that stuck out to me was this: "If you want other rigidbodies to interact with the kinematic rigidbody you need to move it in the FixedUpdate function." That seems to describe what I'm trying to achieve. (?)

I can look into using Lerp and see if it helps. Thx.

Umm...You are doing the moving in FixedUpdate not Update, right? And your rigidbody is set to kinematic?