The bug consist that the anvil is pused horizontaly by a slime block * stinky piston, but after 1 second (even if the anvil touched the floor) it will come back to the launcher, it's hard to explain so here is a video of what happens: https://youtu.be/e83t6dJ_WI0
MC-158732
Broken anvil launcher
Resolved
Awaiting Response
0
The same issue occurs with other gravity blocks, such as sand, as well.