I don't think that is it because when dimitri's dynamites went out (also with Felipe and Paul) Ben was the one to give them a box of new dynamites. How could Dimitri have sabotaged the dynamites when he didn't even see them?
You mean before it explodes? What I understood is that Ben asked for some explosives, DImitri hand his bag to ben and, then, Ben comes back with the same bag, he hand't touched the dynamites because he said he didn't need to used them finally. So it wasn't a new box of dynamite, it was the same bag that dimitry handed him.