I am trying to sequence single circulating tumor cells (CTCs) isolated from mouse blood. I am using Ampli1 kit as a QC before sending the cells to be sequenced. However, I always get the same problem, that I am only able to see 3 out of the 4 bands that should appear after running the samples in the TapeStation. I know that is not a problem of the Ampli1 kit (I have already tried 3 different Ampli1 kits) nor a problem of the cell line (I have also tried 3 different breast cancer cell lines). I thought it might be a problem of the mice, but I get the same problem when processing single cells coming directly from cell culture. I am totally clueless because last time I tried, the 614 bp was also missing in the positive control (I have used that same positive control several times, which is simply human genomic DNA without having any troubles). Have someone experienced anything like that or might have an explanation for this phenomenom?

Thank you in advanced!