The Bug:

Goats will not ram entities that are slightly lower than them, in terms of y level.

Steps to Reproduce:

• Locate a large amount of flat land. (for easier testing).
• Summon a cow that this -0.01 blocks below your position.

/summon minecraft:cow ~ ~-0.01 ~ {NoAI:1b}

• Spawn a goat nearby.
• Alter the goat's data through the use of the following command to make it ram the cow:

/execute as @e[type=minecraft:goat,limit=1,sort=nearest] run data modify entity @s Brain.memories."minecraft:ram_cooldown_ticks".value set value 1

→  Notice how the goat does not and will not ram the cow, as it is -0.01 blocks lower than it.

Information:

If you were to reproduce this with both entities at the same y level, the goat would eventually ram the cow.