Bug in Skill Slots: Last 4 slots not properly acknowledged.
I originally only thought this was a problem that came up in modding, but it seems to extend beyond that, and is easily replicated in the Vanilla game.
Of the 20 skill slots visually shown, only the first 16 are properly "acknowledged". To see this, on character creation, place the skill mechanic in the 17th skill slot, by moving one of the "Basic Human" traits to that one. When you start the game, you *Will* have the option to avoid the Dogman using Mechanic, but you will not have the option to repair the vent. If you place the Mechanic skill in any of the first 16 slots, you will have the option for both actions.
It seems that for some things only the first 16 skill slots are being properly checked, while they are all being checked in other cases. Ideally they would all be checked for all things (so that modding can use all 20 skill slots), but if that's not feasible, then the last four slots should be disabled to reflect the fact that those skills do not offer their proper benefit.
For other examples, "Night Vision" placed in any of the last four slots does not actually give the Night Vision condition, and "Ranged" in any of the last four slots does not give the actual bonuses in combat of the Ranged Skill.