Weird. Only thing I can think is if maybe there's something in the clip files for the animation that requires a target object of a particular height (that or in the posture). Only reason I can see for this is because of the peeing animation stream effect, maybe there's a height requirement, so that the stream hits in the right place.
I mean, you could maybe try extracting the peeing animation and just try to have it play without the posture or something. But then it probably wouldn't have the peeing stream effect (which may not reach the ground even if your attempts were working).
I'm not sure I can be of much more help. I hope you can figure it out though.
