Original description:
Xperia Z5

Standing on an updating slime block that is connected to a sticky piston that's powered by a repeating redstone comparator circuit causes the player to bounce then gets stuck in the slime block in the second bounce instead of bouncing continuously. It also shows the update block particles instead of the slime block ones.

Edit by SuperGeniusZeb: Entities don't bounce off slime blocks that are currently being moved by a piston. During this time, the slime blocks are technically piston extension blocks, so fixing this bug would require making the piston extension block capable of using the bouncy property of slime blocks.