me

confirmed in 15w47c
e: saving entity NBT

my solution
pointcut spam() : (execution(* org.apache.logging.log4j.spi.AbstractLoger.warn(String,..)));

Object around() : spam(){
String arg = (String)thisJoinPoint.getArgs()[0];
if(arg.contains("duplicate UUID") || arg.contains("sending move packet")) return null;
return proceed();}

i found the solution

pointcut spam() : (execution( * org.apache.logging.log4j.spi.AbstractLogger.warn(String,..)));
Object around() : spam() { if(((String)thisJoinPoint.getArgs()[0]).contains("pending"))return null;return proceed();}

150 to 250 spams by minute removed
now i can read my logs 🙂

confirmed here, unable to follow the console messages since the 36d version

not confirmed :
" it's possible it only happens when a chunk is first loaded"
it happend everytime, chunk loaded, unloaded, start stop the server, i suspect a problem with dimensions ( since the method travelToDimension(player, int) changed to travelToDimension(player, int, position) )
see https://bugs.mojang.com/browse/MC-89210 i just opened

ps, i saw this error spam in fresh version AND in my modded version

Yes, this is indeed still an issue. :/

Item breaking sounds of all types are triggered client-side when the game damages and breaks an item, but the server also detects the same conditions to tell other clients to play the item breaking sound.
For example, when you mine a block of stone with your pick, the client realizes that you've broken a block, then damages the client-side version of the pick. The client then realizes that the pick has no durability remaining and plays the break animation and sound. When the server realizes that you've mined the piece of stone, it also damages the server-side version of your pick and detects that you've broken your pick, so it sends packets telling other clients (but not your client) to play the item breaking sound at your location.
With armor, the game damages the armor when it calculates the protection that it gives. However, these calculations are only done server side, so the client never tries to damage its own armor--it just updates the player's inventory according to the server's inventory-change packets, and as such never plays the armor breaking sound and animation.

I assume that similar issues cause hoes, fishing rods, and carrots on sticks not to play their item breaking sounds as well. (As far as I know, those are the only four items to suffer from this issue.)