No box plots after removing primer seq

EDIT: Some new Illumina machines and sequencing chemistries use binned quality scores. NovaSeq does but I'm not sure about older ones like HiSeq. :thinking: See this form post and associated issue on GitHub.

Ah, that explains it: HiSeq uses Illumina's new binned quality scores.

You could try running your reads through DADA2. If does not work try deblur.