Uhh, I dunno if this has been mentioned before, but I really couldn't find any reference to this on the internet. I just recorded it and uploaded it on youtube

http://www.youtube.com/watch?v=zh8gsESQiro

For some reason, when I'm walking in skyrim, then going sideways, the turning animation seems to be missing. (or super-speedy) When I'm overencumbered, the animation seems to work just fine.

This has been bothering me for the past couple of months, I've tried to fix it in multiple ways. Reinstall didn't work, mods definitely aren't the problem. Does anyone even have this bug, or is it just my version of the game? Even better, does anyone know how to fix it, cuz it's totally ruining my 3rd person perspective.

you use mouse to turn, right?
there's a setting in the menu, something like look sensitivity, trial with it, maybe like start with small number.

It has nothing to do with the mouse. The problem is when you're using the keyboard buttons to walk sideways or diagonally like his video showed. Like if you're using the mouse to look around you while using the keyboard W/A/D buttons to keep walking a straight line.

I'm pretty sure everyone has this problem, and as you said, it works as it should when you're encumbered.

could it be the turning speed? If i look, like, really closely, it seems that your character does turn, though way too fast.
Maybe someone should dive into the creation kit, see what they can find.