Group validation error on small test case

[AnantMaheshwari]

./bin/povu gfa2vcf -i simple.gfa > simple.vcf
Group validation failed somewhere!

Hitting this error on this small test case I designed (but getting same error on LPA.gfa in tests/data)

simple.gfa
H VN:Z:1.0
S N1 TTGACCGATGCTAGCTAGGATCCGATGACCTAGGCTAGCTAGGATCCGATG
S N2 ACGTACGTGATCGATCGTACGATCGATCGATGATCGATCGTAGCTAGCTA
S N3a GTTATTTGGGCTAACGCCTCTCTCCACCCTAAATGTTATATCAGCGAGGT
S N3del TCTTCTTGGCCATTGTAGCCTCGGCTGAGAGGAGACGTTCAATCGCCATT
S N3c AAACTCCTACATTGTTAATTTACTTCGATTTATCATCAGTAGATCACCTG
S N4 CCTAGTCGATCGATCGGATCCGTTACGATCGATCGTAGCTAGCTAGCTA
S N5 GGATCCGATGATCGTAGCTAGCTAGATCGATCGATCGATGATCGTACGTA
S INS1 CCGAGGACGTCAAGGATGTTTGTGTATCGAGGCAAGCGCAAATACCTAGT
S N6 TAGCTAGCTAGCTAGGATCCGATCGATCGATGATCGATCGATCGTACGTA
S N7a AGTGATGGTGAGTTCGCCTCGTTGATATGTTGTTGATCCTGGTATAAATTT
S N7inv GGCCTATCACTTACATATCTCTTACATTTATAGTTAAGGCAGCGGATAGAC
S N7c GAGCGCCGAATCAGAACGAGGCCGGCCGCTATATTAGTTGCCTATACCGC
S N8 CGTACGTACGTAGCTAGCTAGCTAGGATCCGATGATCGATCGATCGTACG
S N9a ACTTGCGCGGACGCTGTGCCAAGGCCATTACGGATCGATAGAGGGCACTA
S N9dup TGGTACGGTACGGTACGGTACGGTAC
S N9b GCTTAGGATTTAAAGGGTGACGTTTAAGTGAGTCGCCCGCTAATCAGCAA
S N10 GATCGCGCCGGGCGTTTACTAACGCCCGTCGTTTGATTTCACATCAATCGG
L N1 + N2 + 0M
L N2 + N3a + 0M
L N3a + N3del + 0M
L N3del + N3c + 0M
L N3a + N3c + 0M
L N3c + N4 + 0M
L N4 + N5 + 0M
L N5 + N6 + 0M
L N5 + INS1 + 0M
L INS1 + N6 + 0M
L N6 + N7a + 0M
L N7a + N7c + 0M
L N7a + N7inv - 0M
L N7inv - N7c + 0M
L N7c + N8 + 0M
L N8 + N9a + 0M
L N9a + N9b + 0M
L N9a + N9dup + 0M
L N9dup + N9dup + 0M
L N9dup + N9b + 0M
L N9b + N10 + 0M
P ref_path N1+,N2+,N3a+,N3del+,N3c+,N4+,N5+,N6+,N7a+,N7c+,N8+,N9a+,N9b+,N10+ *
P del_path N1+,N2+,N3a+,N3c+,N4+,N5+,N6+,N7a+,N7c+,N8+,N9a+,N9b+,N10+ *
P ins_path N1+,N2+,N3a+,N3del+,N3c+,N4+,N5+,INS1+,N6+,N7a+,N7c+,N8+,N9a+,N9b+,N10+ *
P inv_path N1+,N2+,N3a+,N3del+,N3c+,N4+,N5+,N6+,N7a+,N7inv-,N7c+,N8+,N9a+,N9b+,N10+ *
P dup_path N1+,N2+,N3a+,N3del+,N3c+,N4+,N5+,N6+,N7a+,N7c+,N8+,N9a+,N9dup+,N9dup+,N9b+,N10+ *
P all_alts N1+,N2+,N3a+,N3c+,N4+,N5+,INS1+,N6+,N7a+,N7inv-,N7c+,N8+,N9a+,N9dup+,N9dup+,N9b+,N10+ *