Automata seem unable to chase down a player.
I've posted this issue in the past, but with far less information. I am now mostly convinced I've found what causes the problem.

The automata will successfully navigate to the position the player was in when the automata first begins to chase them, however once this location is reached the automata will 'get stuck' jittering back and forth in this location (which I believe is caused by it homing in on the same position, constantly overshooting it by 1 block)
The location it saves internally of the 'target player' is likely not updated.
Another great indicator of this theory is that automata seem to cast their spells at this same location, even after the player has moved away.

Sorry that I did not see this sooner. Fortunately (or sadly, considering how long it took) the fix looks very simple.

It will be fixed in the next release 10.9 later today.