Does behaviour change if you move somewhere files /ModScripts/0_O_StatCheckOptimization.rb and /ModScripts/1_O_StatPortraitOptimization.rb?
Those two files from my optimization mod proved to be most problematic with portrait bugs...
If nothing changes then that means it's most likely default behaviour (How's your mood?)
I imagine I can see those files when I open the game up and run it with the console in the background? Yeah, if so I'm not seeing anything of the sort. I may have been a little too quick to determine the bug (or not) was still present in the 0.4.4.0 build, also. I'd gotten a little paranoid after seeing the same portrait for so long that I was sure if I was seeing it then something must be wrong. As is, it's been coming and going in a seemingly as-intended way for several hours now, generally when in a better mood than not. There was definitely something funky up in the older build, though, since the face was consistent across all permutations of stamina, health, food, and mood over the course of an entire in-game week (and I can't say whether or not those specific files you called out were responsible since I ditched the old version, my bad).
So... the problem sorted itself out, whatever it was. If it comes back and I'm sure it's real I'll probably post again, hopefully with more specific criteria for how it triggers, since it seems awfully specific (and judging by my looksee around the board, uncommon).