Steps to reproduce
Have a pool of water, and separately, a pool of lava
Use a spawn egg (pig is a good test subject) on each
The pig will float on top of the water, but will not be placed on top of the lava
Comments 3
it is possible you used the spawn egg aginst the sides accidentally, or you misunderstood the bug, have a deep pit of lava and try to use the egg directly on top of the lava
Unable to reproduce.