Sorry this happened to you:
Inspect at minimum every 10 days to 2 weeks, especially with the Flow Hive: I say that because of the expense involved in obtaining the equipment and the labor intensive process involved in cleaning the Flow frames. With conventional frames at $2.00 per, I just throw them away and start fresh.
I keep many hives in the woods and I do notice more beetles in those hives so I make sure to keep an eye on them and keep them strong.
Another notch in your beekeeping education belt: