Occasionally when grown, dark oak leaves will grow only on one side of the tree. Appears to spawn all the leaves, just not in the right place. This does not always happen when growing a dark oak tree.
How to reproduce:
Execute the following command to spawn a dark oak tree:
/place feature minecraft:dark_oak
or the following command to spawn a pale oak tree:
/place feature minecraft:pale_oak
Repeat step 1 until you find a tree with uncentered leaves.
Expected result:
The leaves would generate roughly in the center of the treetop.
Observed result:
The leaves can sometimes generate several blocks off-center from the treetop.
It's easy to see what is going on when you strip the leaves off one of the trees. The tree top is generating centered around the trunk, but the trunk is going crooked at the top, sort of like an acacia.
I'm adding a screenshot of a stripped dark oak.