Merge indel VCF files

I am merging tons of indel VCF files using vcf-merge. It does not work and I found these VCF files cannot pass the vcf-validation. Is there any way to merge indel VCF files? Thanks!

#CHROM    POS    ID    REF    ALT
1    62297    .    T    TCTTC
1    769138    rs59306077    CAT    C
1    772392    .    ACTTA    TCTTG

The error is

Could not determine the ploidy (nals=4, nvals=3). (TODO: ploidy bigger than 2)
15
 at /apps/software/vcftools/0.1.11/perl/Vcf.pm line 177
        Vcf::throw('Vcf4_0=HASH(0x28b56c0)', 'Could not determine the ploidy (nals=4, nvals=3). (TODO: ploi...', 15) called at /apps/software/vcftools/0.1.11/perl/Vcf.pm line 2408
        VcfReader::guess_ploidy('Vcf4_0=HASH(0x28b56c0)', 4, 3) called at /apps/software/vcftools/0.1.11/perl/Vcf.pm line 1764
        VcfReader::parse_AGtags('Vcf4_0=HASH(0x28b56c0)', 'HASH(0x2f8fc68)', 'HASH(0x27a50d8)', 'GA') called at /apps/software/vcftools/0.1.11/bin/vcf-merge line 453
        main::merge_vcf_files('HASH(0x27def48)') called at /apps/software/vcftools/0.1.11/bin/vcf-merge line 12