Summary:
Vines on a dark oak sometimes replace blocks of leaves with vines, thus forming holes through the trees. This happens both when generating and growing trees from saplings. This bug occurs only with dark oak.

Seed example:

Seed: -732078047
Coordinates: -4310.73 128.00 -8375.95
Coordinates: -4296.21 129.32 -8366.05

Steps to reproduce 1:

1. Create a world with the specified seed.
2. Visit the specified above coordinates.
3. Consider generating dark oak.

Steps to reproduce 2:

1. Create a flat world.
2. Write the command /fill ~1 ~ ~300 ~ ~ ~ sapling 5
3. Set the randomtickspeed game rule to a high value.
4. Consider grown dark oaks with vines.

Observed results:
Vines can sometimes replace leaves on dark oak trees by forming holes near the middle of the tree.

Expected results:
The vines do not replace the leaves on dark oak trees.

Image: