GEE won't run with within-subjects variables PLEASE HELP :)

Hi everyone,

I'm an Ethologist and I'm trying to run a GEE in SPSS looking at the effects of tourism on animals. I have 3 predictors and 1 DV. The predictors are within-subjects variables but I can't get it to run with them included as within-subjects as there are multiple cases where the same animal had the same conditions multiple times and so SPSS sees them as duplicates. Am I doing something wrong? They are different events but happen to contain the same values.

Many thanks in advance!