Turned out I was skipping rooms I don't own inside my main loop. Fixed now. Primoz56 Thank you.

Primoz56 Thank you for your comment.

While blinking between the two rooms, creep.pos shows that the creep is still inside the previous room. 

My creeps are unable to exit room W38S24 to room W38S23. Room W38S23 is the only way out of room W38S24. Room W38S23 is green and has no owner.

creep.moveTo(new RoomPosition(14, 42, 'W38S23'));

This line gives me error -2 (No path to the target could be found). My creep stops moving at the exit blinking in and out between the two rooms. Is this a bug or a problem in my code?