interesting post! I’ve had a similar issue but with a slightly different application… using AddForce to keep my player Character from slipping sideways as it turns at speed in Flying movement mode. For my purposes, this works well… but it doesn’t exactly cancel the slippage.
As you likely, this could get complicated because of all the possible interactions 
It’s VERY interesting that you mention it works exactly with an Actor, but not a Character. If you need it exactly, perhaps consider the interaction of:
- Linear Damping
- Character component Max Acceleration/Braking Friction/Mass/Gravity/Braking Sub Stepping Time/Braking Deceleration/Ground Friction
- Physics volume fluid friction
- How movement input is applied on Tick/Substepping for Characters
