Portal Stone question

[Azrael Maravaile]

I don't know if this has already been mentioned, but another possibility here is that traveling to the same portal stone in a different world takes substantially less of the power than traveling to another portal stone in the same world.

 

Another possibility is that rand wasn't at full strength in the power in TSR when he made his last jump. It is likely that since he couldn't channel at will very well yet that he ended up drawing in much more of the power than he needed to and that was what strained him