I contacted the author and here is the work around for this problem. In short, I have to follow these commands to reach the error (forge step)

$ gff3_merge -d genome_master_datastore_index.log -g
$ mkdir snap_training
$ mv genome.all.gff ./snap_training/
$ cd snap_training/ 
$ maker2zff -n genome.all.gff
$ fathom -validate genome.ann genome.dna
# prints to stdout after validation, several pages long.
$ fathom -gene-stats genome.ann genome.dna
  1365 sequences
  0.413186 avg GC fraction (min=0.339882 max=0.666334)
  24265 genes (plus=12222 minus=12043)
  4313 (0.177746) single-exon
  19952 (0.822254) multi-exon
  181.480927 mean exon (min=1 max=11937)
  792.193176 mean intron (min=30 max=48985)
 $ fathom -categorize 1000 genome.ann genome.dna
 $ fathom -export 1000 uni.ann uni.dna
 $ mkdir parameters
 $ cd parameters
 $ forge ../export.ann ../export.dna
   ZOE ERROR (from forge): impossible error7
   ZOE library version 2013-02-16

If your models have a lot of errors, then the step fathom -export 1000 uni.ann uni.dna will ignore only upto 1000 errors. To ignore more that that, you need to specify the option -export 1000 -plus. this will solve the problem. So use:

 $ fathom -export 1000 -plus uni.ann uni.dna