I am trying to make 9 different fragments (3 tubes of each fragment) from the same template DNA. I am attaching photos (as a PDF) of the results of running all 9 fragments (with 3 tubes) on an agarose gel. The results from the reactions of each fragment come out differently every time. The typical result is a smear, but you can see from the pictures that fragments 8 and 9 show almost nothing on the gel. On fragment 7, one sample gave a lighter band than the other two samples. How can this happen?

I am quite certain it is not a measurement error on my end as I have been running the same reactions for months now. Additionally, I don't believe DNA polymerase or dNTP would be an issue as I just received new stock of these last week.