With Rogue Mechanics getting the neat perk of free Repeater Proficiencies, I think it's time to bring this particular bug back to attention.
When firing off many volleys of bolts with a repeater, quite frequently 1 or 2 shots will simply disappear. Repeaters fire 3 shots per volley, so these lost shots are easily noticeable. Note that these are not shots missed because the bolt misses the target box of the monster. They are shots that simply disappear. The firing animation plays, but nothing is registered on the target.
I did a bit of documenting on this effect, though I can't quite pinpoint what's causing this error to appear simply from observation.
Basically, when firing shots on full auto, lost shots consistently happen by the 13th volley. The 12th volley will have 3 shots, the 13th will have 2 shots, and the 14th will have 1 shot. Then it will reset and go back up to 3 shots.
This isn't always the case. Sometimes shots disappear at more random times, and there will be only 2 shots per volley. However, I'm not sure if this is simply some residual effect from the lost shots happening on the 13th volley.
With a prestige enhancement actually putting a focus back on repeater builds, I really hope the devs will take a look at this issue.