Too few reads used in clonotypes

[NoELJ22]

Hello,

Could you help me understand why there is so low reads used in clonotypes ?
Reads used in clonotypes, percent of total: 13696 (1.73%)

We're working on human PBMC cultured in vitro. The sample isn't stimulated by Ag (Day 0).
For sequencing, the Takara SMART-Seq Human BCR IgG IgM IgA IgD IgE H/K/L Profiling Kit was used. We only used the primer for IgH

The alignment looks good and the overlapping too
Successfully aligned reads: 702545 (88.53%)
Overlapped: 661538 (83.36%)

Code used :

mixcr analyze takara-human-bcr-full-length \
   --remove-step exportClones \
   123-J0-unst_S8_L001_R1_001.fastq.gz 123-J0-unst_S8_L001_R2_001.fastq.gz 123_J0_unstim

mixcr exportReports 123_J0_unstim.clns 123_J0_unstim.report.txt 

I attach the report and fastQC files via filesender:
123_J0_unstim.report.txt
https://filesender.renater.fr/?s=download&token=60478198-bf78-47cd-83db-caf1f722b35a

Thank you for your help

[PoslavskySV]

The issue was resolved via support@milaboratories.com (something went wrong in the wet lab causing missing nucleotides of UMI; workaround was to analyze without UMIs)