https://bugs.winehq.org/show_bug.cgi?id=37705
--- Comment #43 from Sergey Isakov isakov-sl@bk.ru --- Created attachment 63584 --> https://bugs.winehq.org/attachment.cgi?id=63584 saving game before fail
May be this saved game will show you the problem. Unpack and place it into the folder ~/Documents/Might\ &\ Magic\ Heroes\ VI/reloaded/Save/ Run the game and load the saved game. Just next turn will fall into the darkness. It is not a company, it is single scenario.
I am working on creating pure wine with your new patch. But as I already said the bug presents with all wine versions from 1.3 up to 4.1-xxx, with any previous external patches with or without staging. It is not an issue of my enviroment as well as I am not an author of this topic.
Will report soon.