Up from the version Minecraft 1.13 the game render starts to wear down over time. I noticed this bug first under heavy redstone/block/item activity. I recently used an older redstone contraption of mine what was designed by Ilmango (TNT Efficent 2x2 Spruce tree farm). It's basicly a big sawmill to produce wood.

The machine has worked fine up to Minecraft 1.12.2. Now it's killing the game render over time. Integrated server / server ticks are at a fine 20tps but the render still wears down.

I created a test world containing only the machine. It's slightly modified to the latest snapshot.

The test setup destroys all the wood entityes so that is not the cause of the render problems. The saplings are laying arund, but that was fine up to 1.12.2.

To reproduse the render issues:

Just run the attached world in the latest (18w46a) snapshot. Switch on the lever in front of the command block placed at the side of the contraption. Then press the button. The sawmill starts to work, and the only thing is needed is time. In 1 mins the game render starts to wear down.  After a short while freezes will sart, and not long after the game will die. If the sawmill is turned off before it crashes the game the frames will still suffer.

The game render suffers permanent damage. Even if the player turns away or go away the frames will not be restored. In this state facing away from the machine causes to render more frames, but if the player looks at it again frames will drop. (regardless of the entityes)

The attached images are in a timeline presenting the occurance of the problem.

0- the settings, 1- the initial state , 2- the first TNT (or command destroy), 3-16 the developing render breakdown, 17- directly after turning of the sawmill

18- is the final resoult after turning of the sawmill and turned away and back to the farm. Whitout turning away the frramrate will never rise. After some camera turns it will be somewhat restored, but it will never be any close to the original.

EDIT / UPDATE (2019 01.10.) : 19w02a

• The Render issue is still building up in the latest snapshot 19w02a, but now it takes longer to crash the client.
• If the pre crash scenario occures and im still able to switch off the "crash machine" the framerates will somewhat normalize, but the fps will still suffer a bit.

  An overall performance improvement can be confirmed, but the final solution is still a long way to go.

EDIT / UPDATE (2019 04.10.) : 1.14 Pre-Relase 1

      The issue is still present. It's not crashing the client anymore, but it will freeze up for infinity.

      (The attached test setup still works fine in this relase too. Please help confirm the existence of this bug and let it to be fixed before the final relase.)