老师您好！在做变异组的时候有如下问题

命令：gatk --java-options -Xmx2g  HaplotypeCaller -R genome.fasta -I test.bam -O test.g.vcf.gz -ERC GVCF

报错：A USER ERROR has occurred: Bad input: We encountered a non-standard non-IUPAC base in the provided input sequence: '13'

请问这个怎么解决呢？