Bug has existed since the release of 1.15.

Basically, bees will try to path-find thru glass panes and iron bars, causing them to be stuck infinitely because they'll never move. If you hold a flower, they will path find towards the player, but afterwards will then pollinate flowers/crops, and then get stuck trying to go thru glass. This issue is not existent on solid blocks, as in my farm, they only try to go through the panes.