Why when I use two identical characters in the rumble room the keyframes not work well and the characters move simultaneously or remain rigid?
I haven't this issue myself, but I am pretty sure it was fixable with NifSkope. This thread (http://freedomreborn.net/archive/index.php?topic=47381.0) may be of some interest, and it has the link to tommyboy's ghosting mesh tutorial. I notice that tommyboy mentions that recent versions of NifSkope may make the job easier.
Or if you just want to play without going through the fix, you can turn off all shadows in the game preferences. I think this problem mostly occurs with ATI video cards if I remember correctly.
Yes I have an ATI video card. I will try to turn off the shadows.