After escaping from the blockade there are some strange things happening in the game...
[*]It seems that LeChuck is still at the cannon on Spoon Isle, but he is invisible: if you take a look at the first two screenshots you can see a "floating" cannon ball and Guybrush says he don't want to bother him
[*]I already used the fake sea turtle artifact made of pyrite on LeChuck in the forest before the blockade, but now I can still use it on LeChuck when he is "invisible" at he cannon. And everytime I use it on LeChuck (after the fight with pirates cutscene), I find a new one waiting for me at the broken display (see the last screenshot)
Thank you for your help!