Items Glitching/dissapearing in Saved ToolBar between 1.12 and 1.14+

My Saved Toolbar's Items Such as Heads, Books, Named Items, and shulkers with items in them are glitched when switching between 1.12.2 and any version above. the Issue is i have items i originally had on 1.12.2 transferred to 1.15. this was fine but if i try to bring the items through toolbar back to 1.12.2 it would break any items with NBT date such as heads, named items,shulkers and books.