"Sequence Duplication Levels" module still fails after pre-processing Illumina data I want to ask about why the sequence duplication levels are high after I trimmed by using Trimmomatic? I am using the following Trimmomatic operations: HEADCROP = 19 TRAILING = 20 MINLEN = 66.

How can i solve this problem? Thank You.
FastQC assumes that all samples are for whole genome sequencing and will flag them as failed if they differ too much from that assumption. This will, for example, cause essentially all RNA-seq, ChIP-seq, and ATAC-seq samples to fail in one module or another. This is not any cause for concern and is completely expected. Primarily concern yourself with whether all of your samples are similar in their metrics.