I noticed it just now, building a bee-boosted villager crop farm. I enclosed the whole farm in a box of white stained glass, I placed bee nests inside it with bees in them, two flowers on the opposite side (see pictures). The bees exited their nests into the farm, however after doing their job properly for a while, they simply started to fly into the wall of the box, eventually managing to get out through the white stained glass. I triple-checked, I left no holes on the box and at one point I saw a bee fly out through the glass, but i failed to screenshot or record it unfortunately. I sincerely hope that this issue will be addressed, because this way it is quite hard to keep bees in one place. I hope this finds You, and thanks in the name of the Minecraft community in advance!