Weird, i never encountered or read about that glitch
also know the game mechanics quite well,
based on that i could only imagine unlikely reasons
like corrupted files, ram error or OS realted issues
(e.g. when installing Wiz8 in \program files (x86) folder)
How i would try to resolve it:
1st: Backup the saves!
Use tha saves in a new install of the game,
preferably on another(working;) computer, preferably running Win XP,
that should exclude all hardware, install or OS related resons.
If this fails, it may indicate a corrupted save game.
In that case you would have the masters permission
to visit tk421.net/wizardry/files.shtml , get Wizardry 8 Editor(98K) and fix the issue.
Note that a corrupted save may cause more issues which may even be gamebraing.