spindown: I can confirm that the Steam version (v1.7 build 35234) does not have the bug. So it's definitely a problem with the build used on GOG.
Direct compare - that is a "great" info. I would like to know now what happened that GOG distributes faulty version? Now I really hope that there are no other "hidden" bugs connected to this. :/
Can you check size/date of these GOG files below on your Steam version?
Directory of Kings Bounty\data
08-08-2008 | 17:21 | 102˙022˙118 animation.kfs
31-03-2009 | 17:45 | 34˙248˙738 data.kfs
31-03-2009 | 17:45 | 141˙124˙386 interface_textures.kfs
31-03-2009 | 17:45 | 7˙757˙073 loc_data.kfs
08-08-2008 | 17:22 | 55˙596˙703 models.kfs
08-08-2008 | 17:22 | 51˙920˙165 sky.kfs
13-04-2009 | 16:48 | 171˙918˙522 sounds.kfs
08-08-2008 | 17:28 | 324˙299˙505 textures.kfs
Directory of Kings Bounty\sessions\base
31-03-2009 | 17:45 | 828˙345 loc_ses.kfs
31-03-2009 | 17:45 | 6˙365˙376 ses.kfs