My armour and items keep deleting and disappearing when I’m mining a mountain in survival with a diamond pickaxe efficiency 5 haste 2 beacon and it is while I am playing it happens but I have done thurther testing myself and it is only when my inventory hits full with all items I have mined that the object disappears I think it is getting automatically chucked out of my inventory and is invisible because I have seen it automatically chuck stone out before.
How to replicate
1. Find a mountain
2. Get a haste 2 beacon
3. Get a efficiency 5 pickaxe
4. Start mining untill your inventory hits full and have some obvious items to go missing
5. Do this 2 or 3 times then you should get the glitch