When you spawn a panda on a block that is occupied by Bamboo, it will be stuck floating a block above the bottom. I didn't do much investigating, as I went to report the bug immediately. However, I did have my suspicions that it had something to do with either the height of the bamboo or the hitbox change when it reaches around 3-5 blocks tall.
Please attach a screenshot.
Does MC-96319 describe your issue?