Mobs will not burn until they fall/jump above or below y=256 when light level is above 9.

Put the summary of the bug you're having here

What I expected to happen was...:
Mobs should burn at any Y-variable when the light level is above 9.

What actually happened was...:
A mob placed in at Y=256 will not burn until the y-variable falls/jumps above or below y=256.

Steps to Reproduce:
1. Place in a mob at y=256
2. Push mob onto a lower block or strike mob with any weapon.
3. Watch mob burn