PAL, I have however tested the game on TheC64 and Real C64 + Ultimate2+ cartridge without problems. So I think it could be a bug related to fpga64 core for MiST. But I remember that the original Soul Force had this bug on VICE 2.4, then it was fixed. Now it is present on Soul Force X after level 5 for now only on MiST:
Thanks for the quick reply.