The limbs of the characters are not positioned correctly or the body parts don't move properly.

This is a problem that I was not aware of recently since I can't reproduce this. The solution to this is to reset the character's 'FK & IK' Pose

Whenever I start making a scene, I first use Studio Animations to make a initial pose of my characters. And I frequently use KPlug animations, which you can find in Animations> AL F/M, sonyu/houshi. That mod use to be problematic because whenever it updates, you have to re-assign that animation. But that should be fixed according to the author. The new update though which I don't freaking understand seems to caused problems on scenes that uses that animation mod.

SOLUTION

• Select the character
• Go to Animations > Basic > T-Pose

Note: You can choose any animation, but it's highly recommended to choose something close to the scene original animation. Specifically, choose an animation that won't make the spine looks stiff. See the explanation below.

Explanation why you should choose a similar looking animation:

Animations modify the bones itself and changing the default value. When you use FK&IK on a character, not all bones can be control. For example, spine bones can't be modify just by moving the FK handles.

So if the character of my animation originally has a bent spine, then you set its "Animation" to T-Pose, the spine will straighten which makes it looks different.

As you can see from the example below. Let's say the first image is the original pose I did. When I set the animation to T-Pose. The spine and other parts are not properly positioned

Now, with FK&IK still enabled, I change the animation to Titjob > Idle and although there's still a minor difference, everything looks better than the previous one .