I have had this issue for a while. I do work at 110% to 125% when segmenting and also when editing bad segments for a CM because it is easier on my eyes for me to work at larger magnification. I just finished fixing gaps on almost an entire drama. Three of the episodes were OK, even at 125%. The remaining episodes appeared to have an estimated 80% of segments with gaps. Some flashed and some did not. Most of the gaps were large enough to be clearly visible. I did check the video on my cell phone, the Viki web site., and my Roku STV, and there was no flashing after I adjusted the segments.
Additionally, I recently segmented an episode of a drama and the Moderator nicely told me that my timing was horrible. We can all miss a segment or two, but I have never before had my segments so messed up. I mean the timing wasn't even close! I was mortified! I have no idea what happened, as I check my work multiple times. I will try segging and doing remedial editing at 110% and see what happens.
The problem with all of this is the amount of time we, as volunteers, have to spend to ensure quality subtitles. I am certain others feel the pain.