You can skip the entirety of the steamer section 2 and the graveyard section 1 by having the first set of enemies chase you and keep them on screen, (the two sailors and one big firebreather in the steamer section 2 and the ninjas (in 4-1's case, one of the ninjas will just walk off screen leaving you with three ninjas, just wait until the scroll lock is gone and... boom! no enemies to deal with on one of the more harder levels of the game, apart from the stationary knife throwing sailors)) you will be able to walk freely with no screen locks, allowing you to skip the entire level. As long as the enemies are on the screen, the scroll lock is cancelled, and the enemies that were supposed to appear (in the doors and scroll lock areas) don't, the glitch will still be active until you reach the end of the level/ section.

There are some extra technicalities to this tech, but this is the jist of the bug/ tech.