I have a Sar 109t. Holosun HS503G red dot. The bolt that goes through mount and picitinny, snapped on first shot fired. Optic came with high and low mounts. I thought it was a rare defective bolt. I took bolt , from low mount, and reassembled. Once again bolt snapped on first shot. Bolt was not overly tight.I was hoping someone would be able to advise me.