In this section of the guide to Layers of Fear 2, you can find the description of the fourth projector puzzle that has to be solved during the fourth act. Your goal is to materialize a lighthouse and then "rip out" several hearts of mannequins.
You can solve the fourth projector puzzle when you are exploring "the red" rooms in act 4. The main character has to get to the big room with a projector and the mannequins sitting in front of the screen.
Go to the projector and start moving between frames until a figure that looks like a lighthouse (see the picture) appears on the screen.
Go to the lighthouse to travel to a location with its miniature version.
The new location is very dark. However, the lighthouse will illuminate the area. Wait for it to illuminate the area with an interactive heart shown in the picture. Approach it and interact.
A few mannequins will appear around the lighthouse. Approach each one of them and pull out their hearts (hold down the interaction key).
A key will appear next to the lighthouse.
Pick it up and immediately use on the small doors at the base of the lighthouse. You leave this place and move to another (equally strange) place.