Defective front sight - Meprolight TRU-DOT Self Illuminated AR-15 Rifle Night Sights

I bought the mepro true dot sight set. I installed the mepro front sight pin carefully onto a Troy fixed front sight, using a front sight tool. I took it to the range to sight it in and fired 10 rounds. When I looked at the target sheet, I noticed that the bullet holes were all extremely low, which seemed strange to me. When I inspected the front sight, I noticed that the upper part of the front sight pin that spins and holds the tritium had elevated about an eighth of an inch up off the rest of the front sight pin. When I touched the top of the front side pin, it slid back down. I discovered that it slides up and down and is therefore defective. I contacted optics planet and they referred me to mepro. Mepro took my information and then completely ignored me, despite a further email asking what the problem was. Mepro does not back up their warranty for manufacturing defects. I will never buy another mepro product ever again.