I have found two strange physics bugs in the 4.8 Preview 1.
One is if you spawn a physics actor which has simulate physics disabled at location x, then set the location to y and then enable simulate physics, it is again at location x.
Another bug is, if you set simulate physics to off in the details panel, and additionally set simulate physics off in event begin play, then you can’t enable physics later, it just stays disabled.
Here you have a clean repro project for both bugs:
Just hit play, you see the stone falls correctly. Then go into the “Stones” blueprint and connect the exec wire from EventBeginPlay to the stuff inside of the “DoesNotWork” Comment. Then hit play, you see you can’t see the Stone because it’s at location 0/0/0.
For the other bug, connect the wire in Stones back to working and open the Stone blueprint and connect the wire at EventBeginPlay to the SetSimulatePhysics Node. Then hit play, you see the Stone does not move because physics is disabled, even though SetSimulatePhysics(true) gets called in the Stones blueprint.