Very weird, as even though my computer isn't very good I rarely experience lag at the farm, and if I do it's absolutely minimal, I also always get at least a decent fps even at Far render distance.

Best I can advice if your computer is to lower the render to small or tiny before entering the farm, it will definitely give you a good fps boost, and hopefully prevent this killer lag you're talking about. Also closing other possibly unnecessary running apps in your computer may help.(I have experienced something probably similar to what you're describing but in places such as the marketplace, never at any sort of farm).

 

The same thing happens to me whenever I am in my farm town (chillsville), for whatever reason if I am not on tiny render distance I freeze and then crash. Even when I am on far, I get 80 fps but I cannot be in there for more than 30 seconds before it happens.

I doubt it's a bug, it's more than likely just our computers.

 

It just means the minecraft code is a horrid mess and riddled with bugs.

 

If you don't have optifine, try installing optifine. I honestly don't know what else could fix it.