[MOD] Scenarios and campaigns: original, Hammers of Fate.

Hello everyone! I sincerely apologize for bringing up such an old topic from the "depths," but I don't know where else to turn with my question. The issue is this: in the aforementioned campaigns and scenarios of the original game and Hammers of Fate, there is a small but quite unpleasant flaw – in the fortress on the hill, it is impossible to retrain creatures from the main improved version to the alternative version and vice versa (which is quite strange, considering the fact that the freedom of choice regarding the upgrade is preserved). I would like to know what causes this and how it can be fixed.

Colleague, I recommend installing the EWA mod