A similar bug during the alpha (triggered by a specific conversation) could be fixed by walking out of Cyseal through the north or north east gates, and then returning.
It may help Larian determine the cause of this if you save after it happens, and email them that and the previous working save. A couple examples would help, especially if there is one which is reproducible, or even just a small enough time difference to limit the number of things that could be involved.
You can email supportdos@larian.com, with a description of the problem and the report.zip file generated by the
D:OS support tool (for the PC version). The report will contain system and game information, any crash dumps, and your saved games. If file size is an issue, any saves not related to the problem can be deleted.