I highly doubt they knew about it. As Miti said himself, you have to do something specific for a long time to provoke it. And if someone did see something odd, they probably weren't sure what was going on, and reacquired new capture, it was OK and they moved on..
While I understand that type usage is perfectly normal, it is not the usual way people use scopes. I never capture single image and then go back and forth through it for half an hour.
Screen is small and I use Picoscope for that kind of work, or if I didn't have one, would download waveform from scope to PC.
It seems logical not to catch this one early.
But, people put effort in,proved bug is there and work was done to report it and Rigol confirmed it and committed to fix it.
Thanks to those who made it happen.
Now we just need for Rigol to do it's thing.