1. Bushnell DMR (I have one) but the guy next to me at a Rifles Only match in Texas had his erector or reticle break, something inside was rattling. I was the only one who saw where is errant shot went, way low and right and bounced along the ground for a few hundred yards.
2. Tasco World Class 8-32 rimfire benchrest, tracking not following perfectly. Would track after a 1 to 3 shots to the new setting. If you exercised the turrets first, then tracking would be good for a while. The scope was probably 25 to 30 years old, which explains the tracking issue, they get sticky after a while.
3. Bushnell Tactical (with zero stop), not sure exactly which model, Snipers Hide Cup 2015. Was user error, not scope failure. User did not set zero stop correctly and scope lost vertical tracking. When set correctly later in the day, scope returned to tracking correctly.
4. Vortex (PST I believe), parallax not working. Probably a ring over-torque issue but not sure, I didn't find out what the issue was, person was an NRL-22 competitor at our match.
5. Edit: Forgot, Schmidt-Bender PM-II 5-25, elevation turret quit working. The marine snipers said most of theirs quit working at some point, I saw one go down at one of our local matches.