I have some bisulfite PCR primers. They had worked well for us in the past (numerous years and been published). Recently I am getting primer dimer formation from them. I even made fresh dilutions from my stock tube. Old working and new working primer both give primer dimers. I am not using a hot start polymerase but never did in the past and they worked fine. Can primer degrade and give rise to primer dimer? This happened before and was corrected after I made fresh working primers. Maybe my stock is degraded. It's not an issue with optimization. I am worried about a contaminate or degradation of my primers. Suggestions? Comments?