Clear command not working properly

Make a new world in creative, place a command block that says “clear @p rotten_flesh 10”, get 10 rotten flesh from the creative menu, click the button. 

I’ve realized this issue is the same for a lot of items, rotten flesh, copper ingots, string.. I’m sure there’s more but these ones aren’t working at all. I’m trying to make a shop for new players but I can’t do that when the commands are broken. It’s fine in old worlds but it doesn’t work in new worlds. Please fix this asap.