I have been following a published paper for gene amplification and using same primer and thermal conditions but the amplified fragment size in the gel picture is different in my results as compared to that published paper.

However, the fragment length size remained same among 30 random samples I run for PCR. Secondly, when I proceeded with sequencing of about 12 samples, received different lengths of sequences for the same genes among PCR products.

What I need to do please?

I thank you in advance for your kind and motivational suggestions.