Half of my stuff despawned while the other half didn't

I was trying to get my stuff back and when I got to it half of it despwaned and I was really mad. I died in an open feild and there should be no reason why half of it despwaned plz fix this and before anyone says anything I recreated the situation multiple times to account for where my stuff could've gone and it for sure despawned but I don't understand why only half of it did this bug needs to be fixed either the whole thing needs to despawned or none at all