CharacterController Piercing Walls since 2018.3

Hi there! I've got a character controller with a kinematic rigidbody for my player character.

I used to use Continuous Dynamic collisions on the rigidbody, but 2018.3.8f1 is now forcing me to use Speculative mode now. With speculative on, navmesh agents (with kin rigids) pushing against the player causes the player to push right through mesh colliders, such as walls generated using ProBuilder.

I've tried a number of things including increasing the physics timestep, tweaking the character controller skin width, interpolate/extrapolate, and even trying rigidbody discrete mode, but none of that fixes the issue.

Also: this issue was not the case in 2018.1, where i was using Continuous Dynamic mode
Also: i am forced to use continuous speculative because it gets force-selected when i'm using continuous dynamic, even if i change it via script at runtime

Any suggestions?