I'm entirely unclear what you mean.
Like.. I assume you mean heads, and not faces, but even then.. that isn't really a thing that can happen.
I can only assume you got the typical error of having alien backstories on a human, because the race modder assigned the backstories to the faction instead of the race.

The alien heads were reverted to standard human heads. This has happened twice to me so far and no idea how to recreate it.
Only other explanation is that for some reason it somehow gave me humans from a completely alien faction with the exact skin tone, which then reverted to a normal human skin tone upon reloading the save.

Narrowed it down. The game will give me humans from normally all-alien factions.
Is this what you were referring to in your previous answer?
If so what would I need to add/change to create a patch for the race mods?

I'm not entirely certain it's the same thing or even this mod in particular, but I have noticed this happening in my recently made fresh games.

I run an Avali mod, but all of the random pawn spawns (e.g. "Transport Pod Crash" event) only involve "human" pawns.
At first I thought it was just dumb luck or something, but then I started noticing inconsistencies in the stats, factions, backgrounds, etc.

At least some of the spawns should have been Avali. Several even had things that only Avali should* have. Despite that; they were all "human" pawns.

Again, I'm not sure if it's this mod or something with the afore mentioned Avali mod. Regardless, I figured I'd mention it here.

I believe the mod "Real Faction Guest" fixes this issue.