When the actor sits down and stands up it looks like engine plays twice the first frame of the animation. It is noticeable, that the actor twitches between "standup" and "idle" and between "sitdown" and "work".
"sitdown" - actor sits down at the computer
"work" - actor hits the keys of the keyboard (he is sitting)
"standup" - actor stands up from the computer
Here is the exe-file, which demonstrates the bug: http://reptilesquest.mirgames.ru/download/bug.zip
Press F1 - the actor will sit down.
Press F2 - he will stand up.
actor.IdleAnimName = "work";
actor.IdleAnimName = "none";
The actor has no "none" animation. I did this to show the bug better. It is noticeable, that at the end of the "standup" animation the first frame is played again.
Part of .act3d-file