This is part of PhysX and there isn't anything we can do to fix it.
Custom Time Dilation causes PhAT bodies to hover
This is not only happening with vehicles like the original bug described. This is also happening with PhAT skeletal meshes that are moving.
When Time Dilation is in effect, the result of physics calculations become widely different from the result that would be reached when Time Dilation is not in effect. The difference is a big as a car going up a ramp as normal (without Time Dilation) and immediately being shot into the air when the front of the car touches the bottom of the ramp (with Time Dilation).
Project: [Link Removed]
1. Open the attached project
2. Press PIE
3. When the skeletal meshes come to rest, look for any mesh that still has minor movement (if none do, restart and PIE again)
4. Once one of the meshes is mostly settled but still has some minor movement (mostly in limbs), Press the 'F' key to change the Time Dilation to .1
Results: The skeletal mesh will start to rise a bit as if it's floating
Expected: For the mesh to not increase movement but stay settled
OLD VEHICLE STEPS:
1. Download the project in the description and unzip it
2. Right-click the .uproject file to Generate Visual Studio project files and then compile the resulting .sln
3. Launch the game from the .uproject file and load the map inside the Maps folder.
4. Press Play
5. When the cars are nearing the ramp, press Space to turn on Time Dilation.
Result: When the cars collide with the ramp, they are sent flying into the air.
Expected: The same results of not having time dilation : The cars go up the ramp normally.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-23028 in the post.