The execute command is not working correctly: for example, when the command is used to apply a particle on a player, the particle is displayed at the coordinates in the command and not at the player.

Example command in a command block:

/execute @e[type=Player] ~ ~1 ~ /particle witchMagic ~ ~ ~ 0 0 0 0.01 1

Effect:
Particles are displayed at ~ ~1 ~ of the command block.

Command is working correctly in 1.12 - Pre 1