In this live stream, Cedar addresses the issue of brood being laid in the Flow frames, the possible causes for it and how to fix it.
He also answers your questions as they roll in on all things beekeeping.
Have you had this occur? How did you solve it?
We hope this was a helpful live for you 
Two of my bee colony customers (brothers) that were using me as their go-to “bee expert” had this happen to their hives roughly 18-21 months after setting them up.
With brother1, the plastic QE cracked on both sides, allowing the queen up to lay in the Fframes. The bees were getting ready to abscond 3 days after he harvested honey, on account of a hive beetle slime-out. I rescued his colony, he cleaned up the Fframes before he got me to set the hive back up again, before he moved out of the area.
With brother2, it was a different story. I had advised him to leave the hole in the crown board open, then lift the roof once a fortnight, so as to monitor the population, as a swarm prevention measure.
One day he lifted the roof with a huge swarm of bees coming out, which prompted him to inform me that it’s time to split the hive.
Upon removing the roof, I discovered drones, not bees.
In this case the plastic QE was warped, as in this video. It was only luck that he hadn’t attempted to harvest the honey.
As it turned out, the queen got up through the QE, laid a LOT of drone eggs in the Fframes, before making her way back down to the brood box to continue laying down there.
The remedy in both situations was to ditch the plastic QEs in preference for metal ones. I haven’t heard from brother1. however with brother2, the honey wouldn’t flow out of the frames like it used to. He talked about replacing the frames, because of the lack of honey flow.
My guess was, & backed up by reports from users on this forum, that the “silk” of the cocoons blocked the honey from flowing. Cedar said that the silk wouldn’t affect the Fframes.