Minecarts act normally when on normal tracks, but from the moment they hit a Powered track, the player can't ride the cart anymore and the cart starts jiggling around. It looks like the cart is supposed to break but remains stuck in this state.
Environment
Java: Version 8 update 231 (build 1.8.0_231-b11)
Windows 10 Pro Version 1903
You're using activator rails, not powered rails.