I have tried every design for a fish farm and have the same issue with all of the. When I start using an AFK it works as expected but when I catch my first thing and it goes to cast the fishing rod again and it will rapidly cast and reel in the bobber. I tried to give it time and see if it would fix itself but it does not. I have had others try the same design (this is on a realm by the way) and it works just fine for the two who tried it. Is there any known solution to this problem.
Did you bind your right click to a key? If so that's probably the reason why. I had the same thing happen to me when I switched my right click to a key. Later I just did the hold mouse right click and unplug usb trick instead which worked perfectly fine.