Shadow Lords bug (PC)

Each time I try to finish the tutorial missions I get stuck at round 2 after fighting Mimic Jago in the Alps. I choose the item and the guardian, press A to launch the match and the game is stuck forever on a black screen with “round 2” on top (or whatever it says in English) and a flashing box with three slots on the lower right corner.
Did anybody else encounter this issue or knows how to fix it?