It seems to be the last runner in every race (for me anyway). I had a look at the code on github but i am by no means a competent programmer LOL, so I had no insights.
What I did find is the following for another "R" based betfair api bridge.
Maybe someone with more skills than myself can take a look?
have a look at the following link -->
http://code.google.com/p/betfairly/source/browse/trunk/R/funcs.R?r=20
do a search for -->
"if(length(res[[i]]) == 1L){ ## missing prices (happens)"
I hope I haven't upset anyone by posting this..
Happy new year to you all and thank you..