Thank you! I have found an alternative way to make what I'm trying to do. It doesn't solve this particular problem, but I've now achieved my goal I wanted to achieve with this "contraption"
I tried but you can't really throw the trident. It just pops back to its normal position. Could you please post the command you use (if you've tried it)? Because for me it doesn't work. The command I use:
Thanks SUPERIONtheKnight for replying me. It's exaclty what I was trying to do: spec:1b was just an example tag. I think that the problem was indeed the give command (I used something like "give @a stone{tag:{spec:1b}}"). I will try these commands as soon I have the chance!