Error 256 on Baldur's Gate 2 GemRB install

Hi, I tried to install BG2 enahnced (the one from BeamDog) from GOG with the GemRB engine.
The download and installation are smooth, but at the end I have this message:

Started initial process 1409580 from /home/xxx/.cache/lutris/installer/baldurs-gate-ii-complete/unzip /home/xxx/Scaricati/gog/baldurs-gate-ii-complete/gog/ -d /home/xxx/Games/gog/baldurs-gate-ii-complete/tmp data/noarch/*
Start monitoring process.
Archive:  /home/xxx/Scaricati/gog/baldurs-gate-ii-complete/gog/
warning [/home/xxx/Scaricati/gog/baldurs-gate-ii-complete/gog/]:  1000033 extra bytes at beginning or within zipfile
  (attempting to process anyway)
  inflating: /home/xxx/Games/gog/baldurs-gate-ii-complete/tmp/data/noarch/game/scripts/fighter4.BS  
  inflating: /home/xxx/Games/gog/baldurs-gate-ii-complete/tmp/data/noarch/game/scripts/thief2.BS  
  inflating: /home/xxx/Games/gog/baldurs-gate-ii-complete/tmp/data/noarch/  
Monitored process exited.
Initial process has exited (return code: 256)
All processes have quit
Exit with return code 256

If I go to the “tmp” directory created during the install, I can play the game, no issues so far: any clue on how to fix the installer for future users?