when a hopper tries to pull from a mold table, it will first take the ingot mold, if the ingot mold had a cooled ingot it will leave it in the table unremovable unless broken or the next hopper tick is allowed to pass. video below for info

https://medal.tv/games/minecraft/clips/lno4Ua7vViE8nSB4f?invite=cr-MSxodGEsMTMzNDg4MA