When you use the ChangeAnimation function in a script, it seems like the initial value of animpos will be either zero or whatever the last frame is. If animpos was a non-zero number prior to using the ChangeAnimation function, then whenever an animation is selected, animpos will be reset to zero. But if animpos is already a zero, it will be set to whatever the last frame of the new sequence is. This happens whether you ChangeAnimation to the same sequence or a different one. See the included .ged file to see this in action. Note that this does not occur when changing to an animation (as opposed to a sequence)
I guess my question is: is this behavior supposed to be happening? Am I doing something wrong?