Bug: Creep sometimes refuses to spread through open airlocks, or at all.

[ilikesaying]

Description of issue:

Creep will sometimes refuse to spread through airlocks or at all when a creep spreader is placed down.
This happens frequently on the Ishimura Botany airlocks and with Branches.

Difference between expected and actual behavior:

Creep should be able to spread through doors and when they are in the spreading range of a creep spreader that hasn't reached its
maximum creep capacity.

Steps to reproduce:

Have a necromorph break/force open an airlock. Place a creep spreader on existing creep near the airlock
Watch as the creep refuses to spread through the open airlock.

Place branch on existing creep near empty floor.
Watch as the creep doesn't spread.

[Cartlord]

This specificly seems to happen with north/south airlocks with green highlights, but not all of them.