-If a baby bee flies upwards and touches the bottom side of a non-transparent block (stone, logs, dirt, etc) above them, they will take damage.
-They do not take damage if the block above them is transparent (glass, leaves, etc). This leads me to believe it is suffocation damage.
-Only baby bees are affected by this.
I have attached screenshots of an easy setup to reproduce this glitch. Use a spawn egg to spawn many baby bees. The position of the grass and the flower in this setup does not affect the glitch.
Thank you for your report!
We're actually already tracking this issue in MC-159370, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.