Repeat mapping with different result

[BioLaoXu]

Hi，dear developers,I often use HISTAT2 for RNAseq data analysis, but recently I used the same fastq data(RNAseq，PE50) and the same mapping command to analyze and found that the mapping results were different,below is my code:

hisat2 \\
            -x \$INDEX \\
            -1 ${cleanqs[0]} \\
            -2 ${cleanqs[1]} \\
            --met-stderr \\
            --new-summary \\
            --dta \\
            --summary-file ${sample}.hisat2.summary.log \\
            --threads ${task.cpus} \\
            --no-mixed \\
            --no-discordant \\
            | samtools view --threads ${task.cpus} -bS | samtools sort --threads ${task.cpus} -o ${sample}.sort.bam

then,I use samtools stats to calculate the mapping result information for two bam files ，below is my bam statistical result:

I'm curious about what causes the results of the two mapping to be different，could it be caused by seed? looking forward to your response,thanks!