The bug

In a dedicated server, if you set the attribute gravity to 0 or less, you can stay in the air or float upwards. However, if you change it back to the default value (0.08), you will be instantly kicked out of the game.

Steps to Reproduce

1. Set up a dedicated server, using its default settings
2. Make you float upwards by running 

   /attribute @s minecraft:gravity base set -0.01

3. Wait for over 5 seconds
4. Restore the default gravity by running

   /attribute @s minecraft:gravity base set 0.08

Observed Results

You get instantly kicked for flying.

Expected Results

You don't get kicked.